diff --git a/3.0.0.md b/3.0.0.md
index b1c3abfb90..fd56b6c77e 100644
--- a/3.0.0.md
+++ b/3.0.0.md
@@ -28,3 +28,11 @@ Changed `setDriver(DriverInterface $driver)` for all the following platforms:
     - Zend\Db\Adapter\Platform\Postgresql
     - Zend\Db\Adapter\Platform\Sqlite
     - Zend\Db\Adapter\Platform\SqlServer
+
+- Zend\Db\Sql\Platform\PlatformDecoratorInterface
+
+`setSubject()` cannot be type hinted, since implementations use various types 
+
+- Zend\Db\Sql\AbstractSql
+
+`Zend\Db\Sql\Select::resolveTable()` returns an array where as its parent returns a string
diff --git a/src/Sql/AbstractExpression.php b/src/Sql/AbstractExpression.php
index 3fbee7c1c6..73cb1c474d 100644
--- a/src/Sql/AbstractExpression.php
+++ b/src/Sql/AbstractExpression.php
@@ -1,19 +1,29 @@
 <?php
 /**
- * Zend Framework (http://framework.zend.com/)
- *
- * @link      http://github.com/zendframework/zf2 for the canonical source repository
- * @copyright Copyright (c) 2005-2016 Zend Technologies USA Inc. (http://www.zend.com)
- * @license   http://framework.zend.com/license/new-bsd New BSD License
+ * @see       https://github.com/zendframework/zend-db for the canonical source repository
+ * @copyright Copyright (c) 2005-2019 Zend Technologies USA Inc. (https://www.zend.com)
+ * @license   https://github.com/zendframework/zend-db/blob/master/LICENSE.md New BSD License
  */
 
+declare(strict_types=1);
+
 namespace Zend\Db\Sql;
 
+use Zend\Db\Sql\Exception\InvalidArgumentException;
+use function current;
+use function get_class;
+use function gettype;
+use function implode;
+use function in_array;
+use function is_array;
+use function is_int;
+use function is_object;
+use function is_scalar;
+use function key;
+
 abstract class AbstractExpression implements ExpressionInterface
 {
-    /**
-     * @var string[]
-     */
+    /** @var string[] */
     protected $allowedTypes = [
         self::TYPE_IDENTIFIER,
         self::TYPE_LITERAL,
@@ -24,14 +34,13 @@ abstract class AbstractExpression implements ExpressionInterface
     /**
      * Normalize Argument
      *
-     * @param mixed $argument
+     * @param mixed  $argument
      * @param string $defaultType
-     *
      * @return array
      *
      * @throws Exception\InvalidArgumentException
      */
-    protected function normalizeArgument($argument, $defaultType = self::TYPE_VALUE)
+    protected function normalizeArgument($argument, string $defaultType = self::TYPE_VALUE) : array
     {
         if ($argument instanceof ExpressionInterface || $argument instanceof SqlInterface) {
             return $this->buildNormalizedArgument($argument, self::TYPE_VALUE);
@@ -50,20 +59,20 @@ protected function normalizeArgument($argument, $defaultType = self::TYPE_VALUE)
 
             $key = key($argument);
 
-            if (is_integer($key) && ! in_array($value, $this->allowedTypes)) {
+            if (is_int($key) && ! in_array($value, $this->allowedTypes)) {
                 return $this->buildNormalizedArgument($value, $defaultType);
             }
 
             return $this->buildNormalizedArgument($key, $value);
         }
 
-        throw new Exception\InvalidArgumentException(sprintf(
+        throw new InvalidArgumentException(sprintf(
             '$argument should be %s or %s or %s or %s or %s, "%s" given',
             'null',
             'scalar',
             'array',
-            'Zend\Db\Sql\ExpressionInterface',
-            'Zend\Db\Sql\SqlInterface',
+            ExpressionInterface::class,
+            SqlInterface::class,
             is_object($argument) ? get_class($argument) : gettype($argument)
         ));
     }
@@ -71,15 +80,14 @@ protected function normalizeArgument($argument, $defaultType = self::TYPE_VALUE)
     /**
      * @param mixed  $argument
      * @param string $argumentType
-     *
-     * @return array
+     * @return mixed[]
      *
      * @throws Exception\InvalidArgumentException
      */
-    private function buildNormalizedArgument($argument, $argumentType)
+    private function buildNormalizedArgument($argument, string $argumentType) : array
     {
         if (! in_array($argumentType, $this->allowedTypes)) {
-            throw new Exception\InvalidArgumentException(sprintf(
+            throw new InvalidArgumentException(sprintf(
                 'Argument type should be in array(%s)',
                 implode(',', $this->allowedTypes)
             ));
diff --git a/src/Sql/AbstractPreparableSql.php b/src/Sql/AbstractPreparableSql.php
index 6d95f90d84..ca8654a04f 100644
--- a/src/Sql/AbstractPreparableSql.php
+++ b/src/Sql/AbstractPreparableSql.php
@@ -1,27 +1,24 @@
 <?php
 /**
- * Zend Framework (http://framework.zend.com/)
- *
- * @link      http://github.com/zendframework/zf2 for the canonical source repository
- * @copyright Copyright (c) 2005-2016 Zend Technologies USA Inc. (http://www.zend.com)
- * @license   http://framework.zend.com/license/new-bsd New BSD License
+ * @see       https://github.com/zendframework/zend-db for the canonical source repository
+ * @copyright Copyright (c) 2005-2019 Zend Technologies USA Inc. (https://www.zend.com)
+ * @license   https://github.com/zendframework/zend-db/blob/master/LICENSE.md New BSD License
  */
 
+declare(strict_types=1);
+
 namespace Zend\Db\Sql;
 
-use Zend\Db\Adapter\StatementContainerInterface;
 use Zend\Db\Adapter\AdapterInterface;
 use Zend\Db\Adapter\ParameterContainer;
+use Zend\Db\Adapter\StatementContainerInterface;
 
 abstract class AbstractPreparableSql extends AbstractSql implements PreparableSqlInterface
 {
-    /**
-     * {@inheritDoc}
-     *
-     * @return StatementContainerInterface
-     */
-    public function prepareStatement(AdapterInterface $adapter, StatementContainerInterface $statementContainer)
-    {
+    public function prepareStatement(
+        AdapterInterface            $adapter,
+        StatementContainerInterface $statementContainer
+    ) : StatementContainerInterface {
         $parameterContainer = $statementContainer->getParameterContainer();
 
         if (! $parameterContainer instanceof ParameterContainer) {
diff --git a/src/Sql/AbstractSql.php b/src/Sql/AbstractSql.php
index f8935ca44e..8318b72236 100644
--- a/src/Sql/AbstractSql.php
+++ b/src/Sql/AbstractSql.php
@@ -1,59 +1,55 @@
 <?php
 /**
- * Zend Framework (http://framework.zend.com/)
- *
- * @link      http://github.com/zendframework/zf2 for the canonical source repository
- * @copyright Copyright (c) 2005-2016 Zend Technologies USA Inc. (http://www.zend.com)
- * @license   http://framework.zend.com/license/new-bsd New BSD License
+ * @see       https://github.com/zendframework/zend-db for the canonical source repository
+ * @copyright Copyright (c) 2005-2019 Zend Technologies USA Inc. (https://www.zend.com)
+ * @license   https://github.com/zendframework/zend-db/blob/master/LICENSE.md New BSD License
  */
 
+declare(strict_types=1);
+
 namespace Zend\Db\Sql;
 
 use Zend\Db\Adapter\Driver\DriverInterface;
 use Zend\Db\Adapter\ParameterContainer;
 use Zend\Db\Adapter\Platform\PlatformInterface;
-use Zend\Db\Sql\Platform\PlatformDecoratorInterface;
 use Zend\Db\Adapter\Platform\Sql92 as DefaultAdapterPlatform;
+use Zend\Db\Sql\Exception\InvalidArgumentException;
+use Zend\Db\Sql\Exception\RuntimeException;
+use Zend\Db\Sql\Platform\PlatformDecoratorInterface;
+use function count;
+use function get_object_vars;
+use function gettype;
+use function implode;
+use function is_array;
+use function is_string;
+use function preg_replace;
+use function rtrim;
+use function sprintf;
+use function strtoupper;
+use function vsprintf;
 
 abstract class AbstractSql implements SqlInterface
 {
-    /**
-     * Specifications for Sql String generation
-     *
-     * @var string[]|array[]
-     */
+    /** @var string[]|array[] Specifications for Sql String generation */
     protected $specifications = [];
 
-    /**
-     * @var string
-     */
+    /** @var mixed[] */
     protected $processInfo = ['paramPrefix' => '', 'subselectCount' => 0];
 
-    /**
-     * @var array
-     */
+    /** @var array */
     protected $instanceParameterIndex = [];
 
-    /**
-     * {@inheritDoc}
-     */
-    public function getSqlString(PlatformInterface $adapterPlatform = null)
+    public function getSqlString(?PlatformInterface $adapterPlatform = null) : string
     {
-        $adapterPlatform = ($adapterPlatform) ?: new DefaultAdapterPlatform;
+        $adapterPlatform = $adapterPlatform ?? new DefaultAdapterPlatform();
         return $this->buildSqlString($adapterPlatform);
     }
 
-    /**
-     * @param PlatformInterface $platform
-     * @param null|DriverInterface $driver
-     * @param null|ParameterContainer $parameterContainer
-     * @return string
-     */
     protected function buildSqlString(
-        PlatformInterface $platform,
-        DriverInterface $driver = null,
-        ParameterContainer $parameterContainer = null
-    ) {
+        PlatformInterface   $platform,
+        ?DriverInterface    $driver = null,
+        ?ParameterContainer $parameterContainer = null
+    ) : ?string {
         $this->localizeVariables();
 
         $sqls       = [];
@@ -86,39 +82,42 @@ protected function buildSqlString(
      * Render table with alias in from/join parts
      *
      * @todo move TableIdentifier concatenation here
-     * @param string $table
-     * @param string $alias
+     * @param string      $table
+     * @param string|null $alias
      * @return string
      */
-    protected function renderTable($table, $alias = null)
+    protected function renderTable(string $table, ?string $alias = null) : string
     {
         return $table . ($alias ? ' AS ' . $alias : '');
     }
 
     /**
      * @staticvar int $runtimeExpressionPrefix
-     * @param ExpressionInterface $expression
-     * @param PlatformInterface $platform
-     * @param null|DriverInterface $driver
+     *
+     * @param ExpressionInterface     $expression
+     * @param PlatformInterface       $platform
+     * @param null|DriverInterface    $driver
      * @param null|ParameterContainer $parameterContainer
-     * @param null|string $namedParameterPrefix
+     * @param null|string             $namedParameterPrefix
      * @return string
+     *
      * @throws Exception\RuntimeException
      */
     protected function processExpression(
         ExpressionInterface $expression,
-        PlatformInterface $platform,
-        DriverInterface $driver = null,
-        ParameterContainer $parameterContainer = null,
-        $namedParameterPrefix = null
-    ) {
+        PlatformInterface   $platform,
+        ?DriverInterface    $driver = null,
+        ?ParameterContainer $parameterContainer = null,
+        ?string             $namedParameterPrefix = null
+    ) : string {
         $namedParameterPrefix = ! $namedParameterPrefix
             ? $namedParameterPrefix
             : $this->processInfo['paramPrefix'] . $namedParameterPrefix;
+
         // static counter for the number of times this method was invoked across the PHP runtime
         static $runtimeExpressionPrefix = 0;
 
-        if ($parameterContainer && ((! is_string($namedParameterPrefix) || $namedParameterPrefix == ''))) {
+        if ($parameterContainer && (! is_string($namedParameterPrefix) || $namedParameterPrefix === '')) {
             $namedParameterPrefix = sprintf('expr%04dParam', ++$runtimeExpressionPrefix);
         } else {
             $namedParameterPrefix = preg_replace('/\s/', '__', $namedParameterPrefix);
@@ -151,7 +150,7 @@ protected function processExpression(
             }
 
             if (! is_array($part)) {
-                throw new Exception\RuntimeException(
+                throw new RuntimeException(
                     'Elements returned from getExpressionData() array must be a string or array.'
                 );
             }
@@ -159,7 +158,8 @@ protected function processExpression(
             // Process values and types (the middle and last position of the
             // expression data)
             $values = $part[1];
-            $types = isset($part[2]) ? $part[2] : [];
+            $types  = isset($part[2]) ?? [];
+
             foreach ($values as $vIndex => $value) {
                 if (! isset($types[$vIndex])) {
                     continue;
@@ -179,9 +179,9 @@ protected function processExpression(
                         $parameterContainer,
                         $namedParameterPrefix . $vIndex . 'subpart'
                     );
-                } elseif ($type == ExpressionInterface::TYPE_IDENTIFIER) {
+                } elseif ($type === ExpressionInterface::TYPE_IDENTIFIER) {
                     $values[$vIndex] = $platform->quoteIdentifierInFragment($value);
-                } elseif ($type == ExpressionInterface::TYPE_VALUE) {
+                } elseif ($type === ExpressionInterface::TYPE_VALUE) {
                     // if prepareType is set, it means that this particular value must be
                     // passed back to the statement in a way it can be used as a placeholder value
                     if ($parameterContainer) {
@@ -193,7 +193,7 @@ protected function processExpression(
 
                     // if not a preparable statement, simply quote the value and move on
                     $values[$vIndex] = $platform->quoteValue($value);
-                } elseif ($type == ExpressionInterface::TYPE_LITERAL) {
+                } elseif ($type === ExpressionInterface::TYPE_LITERAL) {
                     $values[$vIndex] = $value;
                 }
             }
@@ -208,13 +208,12 @@ protected function processExpression(
 
     /**
      * @param string|array $specifications
-     * @param array $parameters
-     *
+     * @param array        $parameters
      * @return string
      *
      * @throws Exception\RuntimeException
      */
-    protected function createSqlFromSpecificationAndParameters($specifications, $parameters)
+    protected function createSqlFromSpecificationAndParameters($specifications, array $parameters) : string
     {
         if (is_string($specifications)) {
             return vsprintf($specifications, $parameters);
@@ -223,7 +222,7 @@ protected function createSqlFromSpecificationAndParameters($specifications, $par
         $parametersCount = count($parameters);
 
         foreach ($specifications as $specificationString => $paramSpecs) {
-            if ($parametersCount == count($paramSpecs)) {
+            if ($parametersCount === count($paramSpecs)) {
                 break;
             }
 
@@ -231,7 +230,7 @@ protected function createSqlFromSpecificationAndParameters($specifications, $par
         }
 
         if (! isset($specificationString)) {
-            throw new Exception\RuntimeException(
+            throw new RuntimeException(
                 'A number of parameters was found that is not supported by this specification'
             );
         }
@@ -248,7 +247,7 @@ protected function createSqlFromSpecificationAndParameters($specifications, $par
                     }
 
                     if (! isset($paramSpecs[$position][$ppCount])) {
-                        throw new Exception\RuntimeException(sprintf(
+                        throw new RuntimeException(sprintf(
                             'A number of parameters (%d) was found that is not supported by this specification',
                             $ppCount
                         ));
@@ -259,7 +258,7 @@ protected function createSqlFromSpecificationAndParameters($specifications, $par
             } elseif ($paramSpecs[$position] !== null) {
                 $ppCount = count($paramsForPosition);
                 if (! isset($paramSpecs[$position][$ppCount])) {
-                    throw new Exception\RuntimeException(sprintf(
+                    throw new RuntimeException(sprintf(
                         'A number of parameters (%d) was found that is not supported by this specification',
                         $ppCount
                     ));
@@ -269,22 +268,16 @@ protected function createSqlFromSpecificationAndParameters($specifications, $par
                 $topParameters[] = $paramsForPosition;
             }
         }
+
         return vsprintf($specificationString, $topParameters);
     }
 
-    /**
-     * @param Select $subselect
-     * @param PlatformInterface $platform
-     * @param null|DriverInterface $driver
-     * @param null|ParameterContainer $parameterContainer
-     * @return string
-     */
     protected function processSubSelect(
-        Select $subselect,
-        PlatformInterface $platform,
-        DriverInterface $driver = null,
-        ParameterContainer $parameterContainer = null
-    ) {
+        Select              $subselect,
+        PlatformInterface   $platform,
+        ?DriverInterface    $driver = null,
+        ?ParameterContainer $parameterContainer = null
+    ) : string {
         if ($this instanceof PlatformDecoratorInterface) {
             $decorator = clone $this;
             $decorator->setSubject($subselect);
@@ -304,33 +297,26 @@ protected function processSubSelect(
 
             // copy count
             $this->processInfo['subselectCount'] = $decorator->processInfo['subselectCount'];
+
             return $sql;
         }
 
         return $decorator->buildSqlString($platform, $driver, $parameterContainer);
     }
 
-    /**
-     * @param Join[] $joins
-     * @param PlatformInterface $platform
-     * @param null|DriverInterface $driver
-     * @param null|ParameterContainer $parameterContainer
-     * @return null|string[] Null if no joins present, array of JOIN statements
-     *     otherwise
-     * @throws Exception\InvalidArgumentException for invalid JOIN table names.
-     */
     protected function processJoin(
-        Join $joins,
-        PlatformInterface $platform,
-        DriverInterface $driver = null,
-        ParameterContainer $parameterContainer = null
-    ) {
+        Join                $joins,
+        PlatformInterface   $platform,
+        ?DriverInterface    $driver = null,
+        ?ParameterContainer $parameterContainer = null
+    ) : ?array {
         if (! $joins->count()) {
-            return;
+            return null;
         }
 
         // process joins
         $joinSpecArgArray = [];
+
         foreach ($joins->getJoins() as $j => $join) {
             $joinName = null;
             $joinAs = null;
@@ -355,7 +341,7 @@ protected function processJoin(
             } elseif (is_string($joinName) || (is_object($joinName) && is_callable([$joinName, '__toString']))) {
                 $joinName = $platform->quoteIdentifier($joinName);
             } else {
-                throw new Exception\InvalidArgumentException(sprintf(
+                throw new InvalidArgumentException(sprintf(
                     'Join name expected to be Expression|TableIdentifier|Select|string, "%s" given',
                     gettype($joinName)
                 ));
@@ -369,7 +355,7 @@ protected function processJoin(
             // on expression
             // note: for Expression objects, pass them to processExpression with a prefix specific to each join
             // (used for named parameters)
-            if (($join['on'] instanceof ExpressionInterface)) {
+            if ($join['on'] instanceof ExpressionInterface) {
                 $joinSpecArgArray[$j][] = $this->processExpression(
                     $join['on'],
                     $platform,
@@ -391,19 +377,19 @@ protected function processJoin(
 
     /**
      * @param null|array|ExpressionInterface|Select $column
-     * @param PlatformInterface $platform
-     * @param null|DriverInterface $driver
-     * @param null|string $namedParameterPrefix
-     * @param null|ParameterContainer $parameterContainer
+     * @param PlatformInterface                     $platform
+     * @param null|DriverInterface                  $driver
+     * @param null|ParameterContainer               $parameterContainer
+     * @param null|string                           $namedParameterPrefix
      * @return string
      */
     protected function resolveColumnValue(
         $column,
-        PlatformInterface $platform,
-        DriverInterface $driver = null,
-        ParameterContainer $parameterContainer = null,
-        $namedParameterPrefix = null
-    ) {
+        PlatformInterface   $platform,
+        ?DriverInterface    $driver = null,
+        ?ParameterContainer $parameterContainer = null,
+        ?string             $namedParameterPrefix = null
+    ) : string {
         $namedParameterPrefix = ! $namedParameterPrefix
             ? $namedParameterPrefix
             : $this->processInfo['paramPrefix'] . $namedParameterPrefix;
@@ -422,12 +408,16 @@ protected function resolveColumnValue(
         if ($column instanceof ExpressionInterface) {
             return $this->processExpression($column, $platform, $driver, $parameterContainer, $namedParameterPrefix);
         }
+
         if ($column instanceof Select) {
             return '(' . $this->processSubSelect($column, $platform, $driver, $parameterContainer) . ')';
         }
+
         if ($column === null) {
             return 'NULL';
         }
+
+        /** @var string $column */
         return $isIdentifier
                 ? $fromTable . $platform->quoteIdentifierInFragment($column)
                 : $platform->quoteValue($column);
@@ -435,24 +425,25 @@ protected function resolveColumnValue(
 
     /**
      * @param string|TableIdentifier|Select $table
-     * @param PlatformInterface $platform
-     * @param DriverInterface $driver
-     * @param ParameterContainer $parameterContainer
+     * @param PlatformInterface             $platform
+     * @param DriverInterface               $driver
+     * @param ParameterContainer            $parameterContainer
      * @return string
      */
     protected function resolveTable(
         $table,
-        PlatformInterface $platform,
-        DriverInterface $driver = null,
-        ParameterContainer $parameterContainer = null
+        PlatformInterface   $platform,
+        ?DriverInterface    $driver = null,
+        ?ParameterContainer $parameterContainer = null
     ) {
         $schema = null;
+
         if ($table instanceof TableIdentifier) {
-            list($table, $schema) = $table->getTableAndSchema();
+            [$table, $schema] = $table->getTableAndSchema();
         }
 
         if ($table instanceof Select) {
-            $table = '(' . $this->processSubselect($table, $platform, $driver, $parameterContainer) . ')';
+            $table = '(' . $this->processSubSelect($table, $platform, $driver, $parameterContainer) . ')';
         } elseif ($table) {
             $table = $platform->quoteIdentifier($table);
         }
@@ -460,13 +451,14 @@ protected function resolveTable(
         if ($schema && $table) {
             $table = $platform->quoteIdentifier($schema) . $platform->getIdentifierSeparator() . $table;
         }
+
         return $table;
     }
 
     /**
      * Copy variables from the subject into the local properties
      */
-    protected function localizeVariables()
+    protected function localizeVariables() : void
     {
         if (! $this instanceof PlatformDecoratorInterface) {
             return;
diff --git a/src/Sql/Combine.php b/src/Sql/Combine.php
index bedb170f2c..307d9184f6 100644
--- a/src/Sql/Combine.php
+++ b/src/Sql/Combine.php
@@ -1,39 +1,45 @@
 <?php
 /**
- * Zend Framework (http://framework.zend.com/)
- *
- * @link      http://github.com/zendframework/zf2 for the canonical source repository
- * @copyright Copyright (c) 2005-2016 Zend Technologies USA Inc. (http://www.zend.com)
- * @license   http://framework.zend.com/license/new-bsd New BSD License
+ * @see       https://github.com/zendframework/zend-db for the canonical source repository
+ * @copyright Copyright (c) 2005-2019 Zend Technologies USA Inc. (https://www.zend.com)
+ * @license   https://github.com/zendframework/zend-db/blob/master/LICENSE.md New BSD License
  */
 
+declare(strict_types=1);
+
 namespace Zend\Db\Sql;
 
-use Zend\Db\Adapter\Platform\PlatformInterface;
 use Zend\Db\Adapter\Driver\DriverInterface;
 use Zend\Db\Adapter\ParameterContainer;
+use Zend\Db\Adapter\Platform\PlatformInterface;
+use function array_key_exists;
+use function array_merge;
+use function compact;
+use function get_class;
+use function gettype;
+use function is_array;
+use function is_object;
+use function sprintf;
+use function strtoupper;
+use function trim;
 
 /**
  * Combine SQL statement - allows combining multiple select statements into one
  */
 class Combine extends AbstractPreparableSql
 {
-    const COLUMNS = 'columns';
-    const COMBINE = 'combine';
-    const COMBINE_UNION = 'union';
-    const COMBINE_EXCEPT = 'except';
-    const COMBINE_INTERSECT = 'intersect';
+    public const COLUMNS           = 'columns';
+    public const COMBINE           = 'combine';
+    public const COMBINE_UNION     = 'union';
+    public const COMBINE_EXCEPT    = 'except';
+    public const COMBINE_INTERSECT = 'intersect';
 
-    /**
-     * @var string[]
-     */
+    /** @var string[] */
     protected $specifications = [
         self::COMBINE => '%1$s (%2$s) ',
     ];
 
-    /**
-     * @var Select[][]
-     */
+    /** @var Select[][] */
     private $combine = [];
 
     /**
@@ -41,7 +47,7 @@ class Combine extends AbstractPreparableSql
      * @param string            $type
      * @param string            $modifier
      */
-    public function __construct($select = null, $type = self::COMBINE_UNION, $modifier = '')
+    public function __construct($select = null, string $type = self::COMBINE_UNION, string $modifier = '')
     {
         if ($select) {
             $this->combine($select, $type, $modifier);
@@ -52,14 +58,13 @@ public function __construct($select = null, $type = self::COMBINE_UNION, $modifi
      * Create combine clause
      *
      * @param Select|array $select
-     * @param string $type
-     * @param string $modifier
-     *
-     * @return self Provides a fluent interface
+     * @param string       $type
+     * @param string       $modifier
+     * @return $this
      *
      * @throws Exception\InvalidArgumentException
      */
-    public function combine($select, $type = self::COMBINE_UNION, $modifier = '')
+    public function combine($select, string $type = self::COMBINE_UNION, string $modifier = '') : self
     {
         if (is_array($select)) {
             foreach ($select as $combine) {
@@ -83,11 +88,8 @@ public function combine($select, $type = self::COMBINE_UNION, $modifier = '')
             ));
         }
 
-        $this->combine[] = [
-            'select' => $select,
-            'type' => $type,
-            'modifier' => $modifier
-        ];
+        $this->combine[] = compact('select', 'type', 'modifier');
+
         return $this;
     }
 
@@ -96,10 +98,9 @@ public function combine($select, $type = self::COMBINE_UNION, $modifier = '')
      *
      * @param Select|array $select
      * @param string       $modifier
-     *
      * @return self
      */
-    public function union($select, $modifier = '')
+    public function union($select, string $modifier = '') : self
     {
         return $this->combine($select, self::COMBINE_UNION, $modifier);
     }
@@ -109,10 +110,9 @@ public function union($select, $modifier = '')
      *
      * @param Select|array $select
      * @param string       $modifier
-     *
      * @return self
      */
-    public function except($select, $modifier = '')
+    public function except($select, string $modifier = '') : self
     {
         return $this->combine($select, self::COMBINE_EXCEPT, $modifier);
     }
@@ -121,35 +121,27 @@ public function except($select, $modifier = '')
      * Create intersect clause
      *
      * @param Select|array $select
-     * @param string $modifier
+     * @param string       $modifier
      * @return self
      */
-    public function intersect($select, $modifier = '')
+    public function intersect($select, string $modifier = '') : self
     {
         return $this->combine($select, self::COMBINE_INTERSECT, $modifier);
     }
 
-    /**
-     * Build sql string
-     *
-     * @param PlatformInterface  $platform
-     * @param DriverInterface    $driver
-     * @param ParameterContainer $parameterContainer
-     *
-     * @return string
-     */
     protected function buildSqlString(
-        PlatformInterface $platform,
-        DriverInterface $driver = null,
-        ParameterContainer $parameterContainer = null
-    ) {
+        PlatformInterface   $platform,
+        ?DriverInterface    $driver = null,
+        ?ParameterContainer $parameterContainer = null
+    ) : ?string {
         if (! $this->combine) {
-            return;
+            return null;
         }
 
         $sql = '';
+
         foreach ($this->combine as $i => $combine) {
-            $type = $i == 0
+            $type = $i === 0
                     ? ''
                     : strtoupper($combine['type'] . ($combine['modifier'] ? ' ' . $combine['modifier'] : ''));
             $select = $this->processSubSelect($combine['select'], $platform, $driver, $parameterContainer);
@@ -159,13 +151,11 @@ protected function buildSqlString(
                 $select
             );
         }
+
         return trim($sql, ' ');
     }
 
-    /**
-     * @return self Provides a fluent interface
-     */
-    public function alignColumns()
+    public function alignColumns() : self
     {
         if (! $this->combine) {
             return $this;
@@ -189,17 +179,11 @@ public function alignColumns()
             }
             $combine['select']->columns($aligned, false);
         }
+
         return $this;
     }
 
-    /**
-     * Get raw state
-     *
-     * @param string $key
-     *
-     * @return array
-     */
-    public function getRawState($key = null)
+    public function getRawState(?string $key = null) : array
     {
         $rawState = [
             self::COMBINE => $this->combine,
@@ -207,6 +191,7 @@ public function getRawState($key = null)
                                 ? $this->combine[0]['select']->getRawState(self::COLUMNS)
                                 : [],
         ];
+
         return (isset($key) && array_key_exists($key, $rawState)) ? $rawState[$key] : $rawState;
     }
 }
diff --git a/src/Sql/Ddl/AlterTable.php b/src/Sql/Ddl/AlterTable.php
index bee08f9996..dc6ae8dbe4 100644
--- a/src/Sql/Ddl/AlterTable.php
+++ b/src/Sql/Ddl/AlterTable.php
@@ -1,50 +1,45 @@
 <?php
 /**
- * Zend Framework (http://framework.zend.com/)
- *
- * @link      http://github.com/zendframework/zf2 for the canonical source repository
- * @copyright Copyright (c) 2005-2016 Zend Technologies USA Inc. (http://www.zend.com)
- * @license   http://framework.zend.com/license/new-bsd New BSD License
+ * @see       https://github.com/zendframework/zend-db for the canonical source repository
+ * @copyright Copyright (c) 2005-2019 Zend Technologies USA Inc. (https://www.zend.com)
+ * @license   https://github.com/zendframework/zend-db/blob/master/LICENSE.md New BSD License
  */
 
+declare(strict_types=1);
+
 namespace Zend\Db\Sql\Ddl;
 
 use Zend\Db\Adapter\Platform\PlatformInterface;
 use Zend\Db\Sql\AbstractSql;
+use Zend\Db\Sql\Ddl\Column\ColumnInterface;
+use Zend\Db\Sql\Ddl\Constraint\ConstraintInterface;
 use Zend\Db\Sql\TableIdentifier;
+use function array_key_exists;
 
 class AlterTable extends AbstractSql implements SqlInterface
 {
-    const ADD_COLUMNS      = 'addColumns';
-    const ADD_CONSTRAINTS  = 'addConstraints';
-    const CHANGE_COLUMNS   = 'changeColumns';
-    const DROP_COLUMNS     = 'dropColumns';
-    const DROP_CONSTRAINTS = 'dropConstraints';
-    const TABLE            = 'table';
+    public const ADD_COLUMNS      = 'addColumns';
+    public const ADD_CONSTRAINTS  = 'addConstraints';
+    public const CHANGE_COLUMNS   = 'changeColumns';
+    public const DROP_COLUMNS     = 'dropColumns';
+    public const DROP_CONSTRAINTS = 'dropConstraints';
+    public const TABLE            = 'table';
 
-    /**
-     * @var array
-     */
+    private const COMBINEDBY = 'combinedby';
+
+    /** @var array */
     protected $addColumns = [];
 
-    /**
-     * @var array
-     */
+    /** @var array */
     protected $addConstraints = [];
 
-    /**
-     * @var array
-     */
+    /** @var array */
     protected $changeColumns = [];
 
-    /**
-     * @var array
-     */
+    /** @var array */
     protected $dropColumns = [];
 
-    /**
-     * @var array
-     */
+    /** @var array */
     protected $dropConstraints = [];
 
     /**
@@ -54,35 +49,33 @@ class AlterTable extends AbstractSql implements SqlInterface
     protected $specifications = [
         self::TABLE => "ALTER TABLE %1\$s\n",
         self::ADD_COLUMNS  => [
-            "%1\$s" => [
-                [1 => "ADD COLUMN %1\$s,\n", 'combinedby' => ""]
-            ]
+            '%1$s' => [
+                [1 => "ADD COLUMN %1\$s,\n", self::COMBINEDBY => ''],
+            ],
         ],
         self::CHANGE_COLUMNS  => [
-            "%1\$s" => [
-                [2 => "CHANGE COLUMN %1\$s %2\$s,\n", 'combinedby' => ""],
-            ]
+            '%1$s' => [
+                [2 => "CHANGE COLUMN %1\$s %2\$s,\n", self::COMBINEDBY => ''],
+            ],
         ],
         self::DROP_COLUMNS  => [
-            "%1\$s" => [
-                [1 => "DROP COLUMN %1\$s,\n", 'combinedby' => ""],
-            ]
+            '%1$s' => [
+                [1 => "DROP COLUMN %1\$s,\n", self::COMBINEDBY => ''],
+            ],
         ],
         self::ADD_CONSTRAINTS  => [
-            "%1\$s" => [
-                [1 => "ADD %1\$s,\n", 'combinedby' => ""],
-            ]
+            '%1$s' => [
+                [1 => "ADD %1\$s,\n", self::COMBINEDBY => ''],
+            ],
         ],
         self::DROP_CONSTRAINTS  => [
-            "%1\$s" => [
-                [1 => "DROP CONSTRAINT %1\$s,\n", 'combinedby' => ""],
-            ]
-        ]
+            '%1$s' => [
+                [1 => "DROP CONSTRAINT %1\$s,\n", self::COMBINEDBY => ''],
+            ],
+        ],
     ];
 
-    /**
-     * @var string
-     */
+    /** @var string */
     protected $table = '';
 
     /**
@@ -90,14 +83,10 @@ class AlterTable extends AbstractSql implements SqlInterface
      */
     public function __construct($table = '')
     {
-        ($table) ? $this->setTable($table) : null;
+        $table ? $this->setTable($table) : null;
     }
 
-    /**
-     * @param  string $name
-     * @return self Provides a fluent interface
-     */
-    public function setTable($name)
+    public function setTable(string $name) : self
     {
         $this->table = $name;
 
@@ -105,10 +94,10 @@ public function setTable($name)
     }
 
     /**
-     * @param  Column\ColumnInterface $column
-     * @return self Provides a fluent interface
+     * @param ColumnInterface $column
+     * @return $this
      */
-    public function addColumn(Column\ColumnInterface $column)
+    public function addColumn(ColumnInterface $column) : self
     {
         $this->addColumns[] = $column;
 
@@ -116,11 +105,11 @@ public function addColumn(Column\ColumnInterface $column)
     }
 
     /**
-     * @param  string $name
-     * @param  Column\ColumnInterface $column
-     * @return self Provides a fluent interface
+     * @param string          $name
+     * @param ColumnInterface $column
+     * @return $this
      */
-    public function changeColumn($name, Column\ColumnInterface $column)
+    public function changeColumn(string $name, ColumnInterface $column) : self
     {
         $this->changeColumns[$name] = $column;
 
@@ -128,10 +117,10 @@ public function changeColumn($name, Column\ColumnInterface $column)
     }
 
     /**
-     * @param  string $name
-     * @return self Provides a fluent interface
+     * @param string $name
+     * @return $this
      */
-    public function dropColumn($name)
+    public function dropColumn(string $name) : self
     {
         $this->dropColumns[] = $name;
 
@@ -139,10 +128,10 @@ public function dropColumn($name)
     }
 
     /**
-     * @param  string $name
-     * @return self Provides a fluent interface
+     * @param string $name
+     * @return $this
      */
-    public function dropConstraint($name)
+    public function dropConstraint(string $name) : self
     {
         $this->dropConstraints[] = $name;
 
@@ -150,10 +139,10 @@ public function dropConstraint($name)
     }
 
     /**
-     * @param  Constraint\ConstraintInterface $constraint
-     * @return self Provides a fluent interface
+     * @param ConstraintInterface $constraint
+     * @return $this
      */
-    public function addConstraint(Constraint\ConstraintInterface $constraint)
+    public function addConstraint(ConstraintInterface $constraint) : self
     {
         $this->addConstraints[] = $constraint;
 
@@ -161,31 +150,32 @@ public function addConstraint(Constraint\ConstraintInterface $constraint)
     }
 
     /**
-     * @param  string|null $key
+     * @param string|null $key
      * @return array
      */
-    public function getRawState($key = null)
+    public function getRawState(?string $key = null) : array
     {
         $rawState = [
-            self::TABLE => $this->table,
-            self::ADD_COLUMNS => $this->addColumns,
-            self::DROP_COLUMNS => $this->dropColumns,
-            self::CHANGE_COLUMNS => $this->changeColumns,
-            self::ADD_CONSTRAINTS => $this->addConstraints,
+            self::TABLE            => $this->table,
+            self::ADD_COLUMNS      => $this->addColumns,
+            self::DROP_COLUMNS     => $this->dropColumns,
+            self::CHANGE_COLUMNS   => $this->changeColumns,
+            self::ADD_CONSTRAINTS  => $this->addConstraints,
             self::DROP_CONSTRAINTS => $this->dropConstraints,
         ];
 
         return (isset($key) && array_key_exists($key, $rawState)) ? $rawState[$key] : $rawState;
     }
 
-    protected function processTable(PlatformInterface $adapterPlatform = null)
+    protected function processTable(?PlatformInterface $adapterPlatform = null) : array
     {
         return [$this->resolveTable($this->table, $adapterPlatform)];
     }
 
-    protected function processAddColumns(PlatformInterface $adapterPlatform = null)
+    protected function processAddColumns(?PlatformInterface $adapterPlatform = null) : array
     {
         $sqls = [];
+
         foreach ($this->addColumns as $column) {
             $sqls[] = $this->processExpression($column, $adapterPlatform);
         }
@@ -193,22 +183,24 @@ protected function processAddColumns(PlatformInterface $adapterPlatform = null)
         return [$sqls];
     }
 
-    protected function processChangeColumns(PlatformInterface $adapterPlatform = null)
+    protected function processChangeColumns(?PlatformInterface $adapterPlatform = null) : array
     {
         $sqls = [];
+
         foreach ($this->changeColumns as $name => $column) {
             $sqls[] = [
                 $adapterPlatform->quoteIdentifier($name),
-                $this->processExpression($column, $adapterPlatform)
+                $this->processExpression($column, $adapterPlatform),
             ];
         }
 
         return [$sqls];
     }
 
-    protected function processDropColumns(PlatformInterface $adapterPlatform = null)
+    protected function processDropColumns(?PlatformInterface $adapterPlatform = null) : array
     {
         $sqls = [];
+
         foreach ($this->dropColumns as $column) {
             $sqls[] = $adapterPlatform->quoteIdentifier($column);
         }
@@ -216,9 +208,10 @@ protected function processDropColumns(PlatformInterface $adapterPlatform = null)
         return [$sqls];
     }
 
-    protected function processAddConstraints(PlatformInterface $adapterPlatform = null)
+    protected function processAddConstraints(?PlatformInterface $adapterPlatform = null) : array
     {
         $sqls = [];
+
         foreach ($this->addConstraints as $constraint) {
             $sqls[] = $this->processExpression($constraint, $adapterPlatform);
         }
@@ -226,9 +219,10 @@ protected function processAddConstraints(PlatformInterface $adapterPlatform = nu
         return [$sqls];
     }
 
-    protected function processDropConstraints(PlatformInterface $adapterPlatform = null)
+    protected function processDropConstraints(?PlatformInterface $adapterPlatform = null) : array
     {
         $sqls = [];
+
         foreach ($this->dropConstraints as $constraint) {
             $sqls[] = $adapterPlatform->quoteIdentifier($constraint);
         }
diff --git a/src/Sql/Ddl/Column/AbstractLengthColumn.php b/src/Sql/Ddl/Column/AbstractLengthColumn.php
index 59e499d12e..8499fedb02 100644
--- a/src/Sql/Ddl/Column/AbstractLengthColumn.php
+++ b/src/Sql/Ddl/Column/AbstractLengthColumn.php
@@ -1,64 +1,49 @@
 <?php
 /**
- * Zend Framework (http://framework.zend.com/)
- *
- * @link      http://github.com/zendframework/zf2 for the canonical source repository
- * @copyright Copyright (c) 2005-2016 Zend Technologies USA Inc. (http://www.zend.com)
- * @license   http://framework.zend.com/license/new-bsd New BSD License
+ * @see       https://github.com/zendframework/zend-db for the canonical source repository
+ * @copyright Copyright (c) 2005-2019 Zend Technologies USA Inc. (https://www.zend.com)
+ * @license   https://github.com/zendframework/zend-db/blob/master/LICENSE.md New BSD License
  */
 
+declare(strict_types=1);
+
 namespace Zend\Db\Sql\Ddl\Column;
 
 abstract class AbstractLengthColumn extends Column
 {
-    /**
-     * @var int
-     */
+    /** @var int */
     protected $length;
 
-    /**
-     * {@inheritDoc}
-     *
-     * @param int $length
-     */
-    public function __construct($name, $length = null, $nullable = false, $default = null, array $options = [])
-    {
+    public function __construct(
+        ?string $name = null,
+        ?int    $length = null,
+        bool    $nullable = false,
+        $default = null,
+        array   $options = []
+    ) {
         $this->setLength($length);
 
         parent::__construct($name, $nullable, $default, $options);
     }
 
-    /**
-     * @param  int $length
-     * @return self Provides a fluent interface
-     */
-    public function setLength($length)
+    public function setLength(int $length) : self
     {
-        $this->length = (int) $length;
+        $this->length = $length;
 
         return $this;
     }
 
-    /**
-     * @return int
-     */
-    public function getLength()
+    public function getLength() : int
     {
         return $this->length;
     }
 
-    /**
-     * @return string
-     */
-    protected function getLengthExpression()
+    protected function getLengthExpression() : string
     {
         return (string) $this->length;
     }
 
-    /**
-     * @return array
-     */
-    public function getExpressionData()
+    public function getExpressionData() : array
     {
         $data = parent::getExpressionData();
 
diff --git a/src/Sql/Ddl/Column/AbstractPrecisionColumn.php b/src/Sql/Ddl/Column/AbstractPrecisionColumn.php
index 3edba684c5..0a709a2227 100644
--- a/src/Sql/Ddl/Column/AbstractPrecisionColumn.php
+++ b/src/Sql/Ddl/Column/AbstractPrecisionColumn.php
@@ -1,86 +1,60 @@
 <?php
 /**
- * Zend Framework (http://framework.zend.com/)
- *
- * @link      http://github.com/zendframework/zf2 for the canonical source repository
- * @copyright Copyright (c) 2005-2016 Zend Technologies USA Inc. (http://www.zend.com)
- * @license   http://framework.zend.com/license/new-bsd New BSD License
+ * @see       https://github.com/zendframework/zend-db for the canonical source repository
+ * @copyright Copyright (c) 2005-2019 Zend Technologies USA Inc. (https://www.zend.com)
+ * @license   https://github.com/zendframework/zend-db/blob/master/LICENSE.md New BSD License
  */
 
+declare(strict_types=1);
+
 namespace Zend\Db\Sql\Ddl\Column;
 
 abstract class AbstractPrecisionColumn extends AbstractLengthColumn
 {
-    /**
-     * @var int|null
-     */
+    /** @var int|null */
     protected $decimal;
 
-    /**
-     * {@inheritDoc}
-     *
-     * @param int|null $decimal
-     * @param int      $digits
-     */
     public function __construct(
-        $name,
-        $digits = null,
-        $decimal = null,
-        $nullable = false,
+        ?string $name = null,
+        ?int    $digits = null,
+        ?int    $decimal = null,
+        bool    $nullable = false,
         $default = null,
-        array $options = []
+        array   $options = []
     ) {
         $this->setDecimal($decimal);
 
         parent::__construct($name, $digits, $nullable, $default, $options);
     }
 
-    /**
-     * @param  int $digits
-     *
-     * @return self
-     */
-    public function setDigits($digits)
+    public function setDigits(int $digits) : self
     {
         return $this->setLength($digits);
     }
 
-    /**
-     * @return int
-     */
-    public function getDigits()
+    public function getDigits() : int
     {
         return $this->getLength();
     }
 
-    /**
-     * @param int|null $decimal
-     * @return self Provides a fluent interface
-     */
-    public function setDecimal($decimal)
+    public function setDecimal(?int $decimal) : self
     {
         $this->decimal = null === $decimal ? null : (int) $decimal;
 
         return $this;
     }
 
-    /**
-     * @return int|null
-     */
-    public function getDecimal()
+    public function getDecimal() : ?int
     {
         return $this->decimal;
     }
 
-    /**
-     * {@inheritDoc}
-     */
-    protected function getLengthExpression()
+    protected function getLengthExpression() : string
     {
         if ($this->decimal !== null) {
             return $this->length . ',' . $this->decimal;
         }
 
-        return $this->length;
+        return (string) $this->length;
     }
 }
diff --git a/src/Sql/Ddl/Column/AbstractTimestampColumn.php b/src/Sql/Ddl/Column/AbstractTimestampColumn.php
index e71d3791d4..d84e1f31b6 100644
--- a/src/Sql/Ddl/Column/AbstractTimestampColumn.php
+++ b/src/Sql/Ddl/Column/AbstractTimestampColumn.php
@@ -1,14 +1,16 @@
 <?php
 /**
- * Zend Framework (http://framework.zend.com/)
- *
- * @link      http://github.com/zendframework/zf2 for the canonical source repository
- * @copyright Copyright (c) 2005-2016 Zend Technologies USA Inc. (http://www.zend.com)
- * @license   http://framework.zend.com/license/new-bsd New BSD License
+ * @see       https://github.com/zendframework/zend-db for the canonical source repository
+ * @copyright Copyright (c) 2005-2019 Zend Technologies USA Inc. (https://www.zend.com)
+ * @license   https://github.com/zendframework/zend-db/blob/master/LICENSE.md New BSD License
  */
 
+declare(strict_types=1);
+
 namespace Zend\Db\Sql\Ddl\Column;
 
+use function array_merge;
+
 /**
  * Class AbstractTimestampColumn
  * @package Zend\Db\Sql\Ddl\Column
@@ -16,10 +18,7 @@
  */
 abstract class AbstractTimestampColumn extends Column
 {
-    /**
-     * @return array
-     */
-    public function getExpressionData()
+    public function getExpressionData() : array
     {
         $spec = $this->specification;
 
diff --git a/src/Sql/Ddl/Column/BigInteger.php b/src/Sql/Ddl/Column/BigInteger.php
index 83463381d0..554f1b0207 100644
--- a/src/Sql/Ddl/Column/BigInteger.php
+++ b/src/Sql/Ddl/Column/BigInteger.php
@@ -1,18 +1,16 @@
 <?php
 /**
- * Zend Framework (http://framework.zend.com/)
- *
- * @link      http://github.com/zendframework/zf2 for the canonical source repository
- * @copyright Copyright (c) 2005-2016 Zend Technologies USA Inc. (http://www.zend.com)
- * @license   http://framework.zend.com/license/new-bsd New BSD License
+ * @see       https://github.com/zendframework/zend-db for the canonical source repository
+ * @copyright Copyright (c) 2005-2019 Zend Technologies USA Inc. (https://www.zend.com)
+ * @license   https://github.com/zendframework/zend-db/blob/master/LICENSE.md New BSD License
  */
 
+declare(strict_types=1);
+
 namespace Zend\Db\Sql\Ddl\Column;
 
 class BigInteger extends Integer
 {
-    /**
-     * @var string
-     */
+    /** @var string */
     protected $type = 'BIGINT';
 }
diff --git a/src/Sql/Ddl/Column/Binary.php b/src/Sql/Ddl/Column/Binary.php
index b035130897..861a531f1a 100644
--- a/src/Sql/Ddl/Column/Binary.php
+++ b/src/Sql/Ddl/Column/Binary.php
@@ -1,18 +1,16 @@
 <?php
 /**
- * Zend Framework (http://framework.zend.com/)
- *
- * @link      http://github.com/zendframework/zf2 for the canonical source repository
- * @copyright Copyright (c) 2005-2016 Zend Technologies USA Inc. (http://www.zend.com)
- * @license   http://framework.zend.com/license/new-bsd New BSD License
+ * @see       https://github.com/zendframework/zend-db for the canonical source repository
+ * @copyright Copyright (c) 2005-2019 Zend Technologies USA Inc. (https://www.zend.com)
+ * @license   https://github.com/zendframework/zend-db/blob/master/LICENSE.md New BSD License
  */
 
+declare(strict_types=1);
+
 namespace Zend\Db\Sql\Ddl\Column;
 
 class Binary extends AbstractLengthColumn
 {
-    /**
-     * @var string
-     */
+    /** @var string */
     protected $type = 'BINARY';
 }
diff --git a/src/Sql/Ddl/Column/Blob.php b/src/Sql/Ddl/Column/Blob.php
index 4d5a7877b2..2cf4eb50cd 100644
--- a/src/Sql/Ddl/Column/Blob.php
+++ b/src/Sql/Ddl/Column/Blob.php
@@ -1,18 +1,16 @@
 <?php
 /**
- * Zend Framework (http://framework.zend.com/)
- *
- * @link      http://github.com/zendframework/zf2 for the canonical source repository
- * @copyright Copyright (c) 2005-2016 Zend Technologies USA Inc. (http://www.zend.com)
- * @license   http://framework.zend.com/license/new-bsd New BSD License
+ * @see       https://github.com/zendframework/zend-db for the canonical source repository
+ * @copyright Copyright (c) 2005-2019 Zend Technologies USA Inc. (https://www.zend.com)
+ * @license   https://github.com/zendframework/zend-db/blob/master/LICENSE.md New BSD License
  */
 
+declare(strict_types=1);
+
 namespace Zend\Db\Sql\Ddl\Column;
 
 class Blob extends AbstractLengthColumn
 {
-    /**
-     * @var string Change type to blob
-     */
+    /** @var string Change type to blob */
     protected $type = 'BLOB';
 }
diff --git a/src/Sql/Ddl/Column/Boolean.php b/src/Sql/Ddl/Column/Boolean.php
index 6c650e948e..6087bdca02 100644
--- a/src/Sql/Ddl/Column/Boolean.php
+++ b/src/Sql/Ddl/Column/Boolean.php
@@ -1,31 +1,16 @@
 <?php
 /**
- * Zend Framework (http://framework.zend.com/)
- *
- * @link      http://github.com/zendframework/zf2 for the canonical source repository
- * @copyright Copyright (c) 2005-2016 Zend Technologies USA Inc. (http://www.zend.com)
- * @license   http://framework.zend.com/license/new-bsd New BSD License
+ * @see       https://github.com/zendframework/zend-db for the canonical source repository
+ * @copyright Copyright (c) 2005-2019 Zend Technologies USA Inc. (https://www.zend.com)
+ * @license   https://github.com/zendframework/zend-db/blob/master/LICENSE.md New BSD License
  */
 
+declare(strict_types=1);
+
 namespace Zend\Db\Sql\Ddl\Column;
 
 class Boolean extends Column
 {
-    /**
-     * @var string
-     */
+    /** @var string */
     protected $type = 'BOOLEAN';
-
-    /**
-     * {@inheritDoc}
-     */
-    protected $isNullable = false;
-
-    /**
-     * {@inheritDoc}
-     */
-    public function setNullable($nullable)
-    {
-        return parent::setNullable(false);
-    }
 }
diff --git a/src/Sql/Ddl/Column/Char.php b/src/Sql/Ddl/Column/Char.php
index 7e7199bcd0..a8d7c46281 100644
--- a/src/Sql/Ddl/Column/Char.php
+++ b/src/Sql/Ddl/Column/Char.php
@@ -1,18 +1,16 @@
 <?php
 /**
- * Zend Framework (http://framework.zend.com/)
- *
- * @link http://github.com/zendframework/zf2 for the canonical source repository
- * @copyright Copyright (c) 2005-2016 Zend Technologies USA Inc. (http://www.zend.com)
- * @license http://framework.zend.com/license/new-bsd New BSD License
+ * @see       https://github.com/zendframework/zend-db for the canonical source repository
+ * @copyright Copyright (c) 2005-2019 Zend Technologies USA Inc. (https://www.zend.com)
+ * @license   https://github.com/zendframework/zend-db/blob/master/LICENSE.md New BSD License
  */
 
+declare(strict_types=1);
+
 namespace Zend\Db\Sql\Ddl\Column;
 
 class Char extends AbstractLengthColumn
 {
-    /**
-     * @var string
-     */
+    /** @var string */
     protected $type = 'CHAR';
 }
diff --git a/src/Sql/Ddl/Column/Column.php b/src/Sql/Ddl/Column/Column.php
index 18634194cf..96d25eeb24 100644
--- a/src/Sql/Ddl/Column/Column.php
+++ b/src/Sql/Ddl/Column/Column.php
@@ -1,60 +1,41 @@
 <?php
 /**
- * Zend Framework (http://framework.zend.com/)
- *
- * @link      http://github.com/zendframework/zf2 for the canonical source repository
- * @copyright Copyright (c) 2005-2016 Zend Technologies USA Inc. (http://www.zend.com)
- * @license   http://framework.zend.com/license/new-bsd New BSD License
+ * @see       https://github.com/zendframework/zend-db for the canonical source repository
+ * @copyright Copyright (c) 2005-2019 Zend Technologies USA Inc. (https://www.zend.com)
+ * @license   https://github.com/zendframework/zend-db/blob/master/LICENSE.md New BSD License
  */
 
+declare(strict_types=1);
+
 namespace Zend\Db\Sql\Ddl\Column;
 
 use Zend\Db\Sql\Ddl\Constraint\ConstraintInterface;
+use function array_merge;
 
 class Column implements ColumnInterface
 {
-    /**
-     * @var null|string|int
-     */
+    /** @var null|string|int */
     protected $default;
 
-    /**
-     * @var bool
-     */
+    /** @var bool */
     protected $isNullable = false;
 
-    /**
-     * @var string
-     */
+    /** @var string|null */
     protected $name = '';
 
-    /**
-     * @var array
-     */
+    /** @var array */
     protected $options = [];
 
-    /**
-     * @var ConstraintInterface[]
-     */
+    /** @var ConstraintInterface[] */
     protected $constraints = [];
 
-    /**
-     * @var string
-     */
+    /** @var string */
     protected $specification = '%s %s';
 
-    /**
-     * @var string
-     */
+    /** @var string */
     protected $type = 'INTEGER';
 
-    /**
-     * @param null|string $name
-     * @param bool        $nullable
-     * @param mixed|null  $default
-     * @param mixed[]     $options
-     */
-    public function __construct($name = null, $nullable = false, $default = null, array $options = [])
+    public function __construct(?string $name = null, bool $nullable = false, $default = null, array $options = [])
     {
         $this->setName($name);
         $this->setNullable($nullable);
@@ -62,49 +43,38 @@ public function __construct($name = null, $nullable = false, $default = null, ar
         $this->setOptions($options);
     }
 
-    /**
-     * @param  string $name
-     * @return self Provides a fluent interface
-     */
-    public function setName($name)
+    public function setName(?string $name) : self
     {
-        $this->name = (string) $name;
+        $this->name = $name;
+
         return $this;
     }
 
-    /**
-     * @return null|string
-     */
-    public function getName()
+    public function getName() : string
     {
         return $this->name;
     }
 
-    /**
-     * @param  bool $nullable
-     * @return self Provides a fluent interface
-     */
-    public function setNullable($nullable)
+    public function setNullable(bool $nullable) : self
     {
-        $this->isNullable = (bool) $nullable;
+        $this->isNullable = $nullable;
+
         return $this;
     }
 
-    /**
-     * @return bool
-     */
-    public function isNullable()
+    public function isNullable() : bool
     {
         return $this->isNullable;
     }
 
     /**
-     * @param  null|string|int $default
-     * @return self Provides a fluent interface
+     * @param null|string|int $default
+     * @return $this
      */
-    public function setDefault($default)
+    public function setDefault($default) : self
     {
         $this->default = $default;
+
         return $this;
     }
 
@@ -116,51 +86,33 @@ public function getDefault()
         return $this->default;
     }
 
-    /**
-     * @param  array $options
-     * @return self Provides a fluent interface
-     */
-    public function setOptions(array $options)
+    public function setOptions(array $options) : self
     {
         $this->options = $options;
+
         return $this;
     }
 
-    /**
-     * @param  string $name
-     * @param  string $value
-     * @return self Provides a fluent interface
-     */
-    public function setOption($name, $value)
+    public function setOption(string $name, string $value) : self
     {
         $this->options[$name] = $value;
+
         return $this;
     }
 
-    /**
-     * @return array
-     */
-    public function getOptions()
+    public function getOptions() : array
     {
         return $this->options;
     }
 
-    /**
-     * @param ConstraintInterface $constraint
-     *
-     * @return self Provides a fluent interface
-     */
-    public function addConstraint(ConstraintInterface $constraint)
+    public function addConstraint(ConstraintInterface $constraint) : self
     {
         $this->constraints[] = $constraint;
 
         return $this;
     }
 
-    /**
-     * @return array
-     */
-    public function getExpressionData()
+    public function getExpressionData() : array
     {
         $spec = $this->specification;
 
diff --git a/src/Sql/Ddl/Column/ColumnInterface.php b/src/Sql/Ddl/Column/ColumnInterface.php
index ff38b5a080..b52d43cf52 100644
--- a/src/Sql/Ddl/Column/ColumnInterface.php
+++ b/src/Sql/Ddl/Column/ColumnInterface.php
@@ -1,12 +1,12 @@
 <?php
 /**
- * Zend Framework (http://framework.zend.com/)
- *
- * @link      http://github.com/zendframework/zf2 for the canonical source repository
- * @copyright Copyright (c) 2005-2016 Zend Technologies USA Inc. (http://www.zend.com)
- * @license   http://framework.zend.com/license/new-bsd New BSD License
+ * @see       https://github.com/zendframework/zend-db for the canonical source repository
+ * @copyright Copyright (c) 2005-2019 Zend Technologies USA Inc. (https://www.zend.com)
+ * @license   https://github.com/zendframework/zend-db/blob/master/LICENSE.md New BSD License
  */
 
+declare(strict_types=1);
+
 namespace Zend\Db\Sql\Ddl\Column;
 
 use Zend\Db\Sql\ExpressionInterface;
@@ -18,23 +18,14 @@
  */
 interface ColumnInterface extends ExpressionInterface
 {
-    /**
-     * @return string
-     */
-    public function getName();
+    public function getName() : string;
 
-    /**
-     * @return bool
-     */
-    public function isNullable();
+    public function isNullable() : bool;
 
     /**
      * @return null|string|int
      */
     public function getDefault();
 
-    /**
-     * @return array
-     */
-    public function getOptions();
+    public function getOptions() : array;
 }
diff --git a/src/Sql/Ddl/Column/Date.php b/src/Sql/Ddl/Column/Date.php
index 7fe3969927..ad76bf45d3 100644
--- a/src/Sql/Ddl/Column/Date.php
+++ b/src/Sql/Ddl/Column/Date.php
@@ -1,18 +1,16 @@
 <?php
 /**
- * Zend Framework (http://framework.zend.com/)
- *
- * @link      http://github.com/zendframework/zf2 for the canonical source repository
- * @copyright Copyright (c) 2005-2016 Zend Technologies USA Inc. (http://www.zend.com)
- * @license   http://framework.zend.com/license/new-bsd New BSD License
+ * @see       https://github.com/zendframework/zend-db for the canonical source repository
+ * @copyright Copyright (c) 2005-2019 Zend Technologies USA Inc. (https://www.zend.com)
+ * @license   https://github.com/zendframework/zend-db/blob/master/LICENSE.md New BSD License
  */
 
+declare(strict_types=1);
+
 namespace Zend\Db\Sql\Ddl\Column;
 
 class Date extends Column
 {
-    /**
-     * @var string
-     */
+    /** @var string */
     protected $type = 'DATE';
 }
diff --git a/src/Sql/Ddl/Column/Datetime.php b/src/Sql/Ddl/Column/Datetime.php
index 955653e883..3b1ba4b27b 100644
--- a/src/Sql/Ddl/Column/Datetime.php
+++ b/src/Sql/Ddl/Column/Datetime.php
@@ -1,18 +1,16 @@
 <?php
 /**
- * Zend Framework (http://framework.zend.com/)
- *
- * @link      http://github.com/zendframework/zf2 for the canonical source repository
- * @copyright Copyright (c) 2005-2016 Zend Technologies USA Inc. (http://www.zend.com)
- * @license   http://framework.zend.com/license/new-bsd New BSD License
+ * @see       https://github.com/zendframework/zend-db for the canonical source repository
+ * @copyright Copyright (c) 2005-2019 Zend Technologies USA Inc. (https://www.zend.com)
+ * @license   https://github.com/zendframework/zend-db/blob/master/LICENSE.md New BSD License
  */
 
+declare(strict_types=1);
+
 namespace Zend\Db\Sql\Ddl\Column;
 
 class Datetime extends Column
 {
-    /**
-     * @var string
-     */
+    /** @var string */
     protected $type = 'DATETIME';
 }
diff --git a/src/Sql/Ddl/Column/Decimal.php b/src/Sql/Ddl/Column/Decimal.php
index 654d494407..c8605d1a1e 100644
--- a/src/Sql/Ddl/Column/Decimal.php
+++ b/src/Sql/Ddl/Column/Decimal.php
@@ -1,18 +1,16 @@
 <?php
 /**
- * Zend Framework (http://framework.zend.com/)
- *
- * @link      http://github.com/zendframework/zf2 for the canonical source repository
- * @copyright Copyright (c) 2005-2016 Zend Technologies USA Inc. (http://www.zend.com)
- * @license   http://framework.zend.com/license/new-bsd New BSD License
+ * @see       https://github.com/zendframework/zend-db for the canonical source repository
+ * @copyright Copyright (c) 2005-2019 Zend Technologies USA Inc. (https://www.zend.com)
+ * @license   https://github.com/zendframework/zend-db/blob/master/LICENSE.md New BSD License
  */
 
+declare(strict_types=1);
+
 namespace Zend\Db\Sql\Ddl\Column;
 
 class Decimal extends AbstractPrecisionColumn
 {
-    /**
-     * @var string
-     */
+    /** @var string */
     protected $type = 'DECIMAL';
 }
diff --git a/src/Sql/Ddl/Column/Float.php b/src/Sql/Ddl/Column/Float.php
index a67f857568..d58def5338 100644
--- a/src/Sql/Ddl/Column/Float.php
+++ b/src/Sql/Ddl/Column/Float.php
@@ -1,14 +1,17 @@
 <?php
 /**
- * Zend Framework (http://framework.zend.com/)
- *
- * @link      http://github.com/zendframework/zf2 for the canonical source repository
- * @copyright Copyright (c) 2005-2016 Zend Technologies USA Inc. (http://www.zend.com)
- * @license   http://framework.zend.com/license/new-bsd New BSD License
+ * @see       https://github.com/zendframework/zend-db for the canonical source repository
+ * @copyright Copyright (c) 2005-2019 Zend Technologies USA Inc. (https://www.zend.com)
+ * @license   https://github.com/zendframework/zend-db/blob/master/LICENSE.md New BSD License
  */
 
+declare(strict_types=1);
+
 namespace Zend\Db\Sql\Ddl\Column;
 
+use function trigger_error;
+use function sprintf;
+
 /**
  * Stub class for backwards compatibility.
  *
@@ -27,12 +30,12 @@ class Float extends Floating
      * Raises a deprecation notice.
      */
     public function __construct(
-        $name,
-        $digits = null,
-        $decimal = null,
-        $nullable = false,
+        string $name = '',
+        ?int   $digits = null,
+        ?int   $decimal = null,
+        bool   $nullable = false,
         $default = null,
-        array $options = []
+        array  $options = []
     ) {
         trigger_error(
             sprintf(
diff --git a/src/Sql/Ddl/Column/Floating.php b/src/Sql/Ddl/Column/Floating.php
index a6a9aa1568..6cb892bda4 100644
--- a/src/Sql/Ddl/Column/Floating.php
+++ b/src/Sql/Ddl/Column/Floating.php
@@ -1,12 +1,12 @@
 <?php
 /**
- * Zend Framework (http://framework.zend.com/)
- *
- * @link      http://github.com/zendframework/zf2 for the canonical source repository
- * @copyright Copyright (c) 2005-2016 Zend Technologies USA Inc. (http://www.zend.com)
- * @license   http://framework.zend.com/license/new-bsd New BSD License
+ * @see       https://github.com/zendframework/zend-db for the canonical source repository
+ * @copyright Copyright (c) 2005-2019 Zend Technologies USA Inc. (https://www.zend.com)
+ * @license   https://github.com/zendframework/zend-db/blob/master/LICENSE.md New BSD License
  */
 
+declare(strict_types=1);
+
 namespace Zend\Db\Sql\Ddl\Column;
 
 /**
@@ -17,8 +17,6 @@
  */
 class Floating extends AbstractPrecisionColumn
 {
-    /**
-     * @var string
-     */
+    /** @var string */
     protected $type = 'FLOAT';
 }
diff --git a/src/Sql/Ddl/Column/Integer.php b/src/Sql/Ddl/Column/Integer.php
index b24d2fd5a1..f2dbffa050 100644
--- a/src/Sql/Ddl/Column/Integer.php
+++ b/src/Sql/Ddl/Column/Integer.php
@@ -1,20 +1,18 @@
 <?php
 /**
- * Zend Framework (http://framework.zend.com/)
- *
- * @link      http://github.com/zendframework/zf2 for the canonical source repository
- * @copyright Copyright (c) 2005-2016 Zend Technologies USA Inc. (http://www.zend.com)
- * @license   http://framework.zend.com/license/new-bsd New BSD License
+ * @see       https://github.com/zendframework/zend-db for the canonical source repository
+ * @copyright Copyright (c) 2005-2019 Zend Technologies USA Inc. (https://www.zend.com)
+ * @license   https://github.com/zendframework/zend-db/blob/master/LICENSE.md New BSD License
  */
 
+declare(strict_types=1);
+
 namespace Zend\Db\Sql\Ddl\Column;
 
 class Integer extends Column
 {
-    /**
-     * @return array
-     */
-    public function getExpressionData()
+
+    public function getExpressionData() : array
     {
         $data    = parent::getExpressionData();
         $options = $this->getOptions();
diff --git a/src/Sql/Ddl/Column/Text.php b/src/Sql/Ddl/Column/Text.php
index 53ceafaa02..06b21d64e0 100644
--- a/src/Sql/Ddl/Column/Text.php
+++ b/src/Sql/Ddl/Column/Text.php
@@ -1,18 +1,16 @@
 <?php
 /**
- * Zend Framework (http://framework.zend.com/)
- *
- * @link      http://github.com/zendframework/zf2 for the canonical source repository
- * @copyright Copyright (c) 2005-2016 Zend Technologies USA Inc. (http://www.zend.com)
- * @license   http://framework.zend.com/license/new-bsd New BSD License
+ * @see       https://github.com/zendframework/zend-db for the canonical source repository
+ * @copyright Copyright (c) 2005-2019 Zend Technologies USA Inc. (https://www.zend.com)
+ * @license   https://github.com/zendframework/zend-db/blob/master/LICENSE.md New BSD License
  */
 
+declare(strict_types=1);
+
 namespace Zend\Db\Sql\Ddl\Column;
 
 class Text extends AbstractLengthColumn
 {
-    /**
-     * @var string
-     */
+    /** @var string */
     protected $type = 'TEXT';
 }
diff --git a/src/Sql/Ddl/Column/Time.php b/src/Sql/Ddl/Column/Time.php
index 7de591301f..812e21f179 100644
--- a/src/Sql/Ddl/Column/Time.php
+++ b/src/Sql/Ddl/Column/Time.php
@@ -1,18 +1,16 @@
 <?php
 /**
- * Zend Framework (http://framework.zend.com/)
- *
- * @link      http://github.com/zendframework/zf2 for the canonical source repository
- * @copyright Copyright (c) 2005-2016 Zend Technologies USA Inc. (http://www.zend.com)
- * @license   http://framework.zend.com/license/new-bsd New BSD License
+ * @see       https://github.com/zendframework/zend-db for the canonical source repository
+ * @copyright Copyright (c) 2005-2019 Zend Technologies USA Inc. (https://www.zend.com)
+ * @license   https://github.com/zendframework/zend-db/blob/master/LICENSE.md New BSD License
  */
 
+declare(strict_types=1);
+
 namespace Zend\Db\Sql\Ddl\Column;
 
 class Time extends Column
 {
-    /**
-     * @var string
-     */
+    /** @var string */
     protected $type = 'TIME';
 }
diff --git a/src/Sql/Ddl/Column/Timestamp.php b/src/Sql/Ddl/Column/Timestamp.php
index d59826bf94..9a55cbbe81 100644
--- a/src/Sql/Ddl/Column/Timestamp.php
+++ b/src/Sql/Ddl/Column/Timestamp.php
@@ -1,18 +1,16 @@
 <?php
 /**
- * Zend Framework (http://framework.zend.com/)
- *
- * @link      http://github.com/zendframework/zf2 for the canonical source repository
- * @copyright Copyright (c) 2005-2016 Zend Technologies USA Inc. (http://www.zend.com)
- * @license   http://framework.zend.com/license/new-bsd New BSD License
+ * @see       https://github.com/zendframework/zend-db for the canonical source repository
+ * @copyright Copyright (c) 2005-2019 Zend Technologies USA Inc. (https://www.zend.com)
+ * @license   https://github.com/zendframework/zend-db/blob/master/LICENSE.md New BSD License
  */
 
+declare(strict_types=1);
+
 namespace Zend\Db\Sql\Ddl\Column;
 
 class Timestamp extends AbstractTimestampColumn
 {
-    /**
-     * @var string
-     */
+    /** @var string */
     protected $type = 'TIMESTAMP';
 }
diff --git a/src/Sql/Ddl/Column/Varbinary.php b/src/Sql/Ddl/Column/Varbinary.php
index 4b8e3e63dc..ba780e49ae 100644
--- a/src/Sql/Ddl/Column/Varbinary.php
+++ b/src/Sql/Ddl/Column/Varbinary.php
@@ -1,18 +1,16 @@
 <?php
 /**
- * Zend Framework (http://framework.zend.com/)
- *
- * @link      http://github.com/zendframework/zf2 for the canonical source repository
- * @copyright Copyright (c) 2005-2016 Zend Technologies USA Inc. (http://www.zend.com)
- * @license   http://framework.zend.com/license/new-bsd New BSD License
+ * @see       https://github.com/zendframework/zend-db for the canonical source repository
+ * @copyright Copyright (c) 2005-2019 Zend Technologies USA Inc. (https://www.zend.com)
+ * @license   https://github.com/zendframework/zend-db/blob/master/LICENSE.md New BSD License
  */
 
+declare(strict_types=1);
+
 namespace Zend\Db\Sql\Ddl\Column;
 
 class Varbinary extends AbstractLengthColumn
 {
-    /**
-     * @var string
-     */
+    /** @var string */
     protected $type = 'VARBINARY';
 }
diff --git a/src/Sql/Ddl/Column/Varchar.php b/src/Sql/Ddl/Column/Varchar.php
index 8a90ac7807..92718ef009 100644
--- a/src/Sql/Ddl/Column/Varchar.php
+++ b/src/Sql/Ddl/Column/Varchar.php
@@ -1,18 +1,16 @@
 <?php
 /**
- * Zend Framework (http://framework.zend.com/)
- *
- * @link      http://github.com/zendframework/zf2 for the canonical source repository
- * @copyright Copyright (c) 2005-2016 Zend Technologies USA Inc. (http://www.zend.com)
- * @license   http://framework.zend.com/license/new-bsd New BSD License
+ * @see       https://github.com/zendframework/zend-db for the canonical source repository
+ * @copyright Copyright (c) 2005-2019 Zend Technologies USA Inc. (https://www.zend.com)
+ * @license   https://github.com/zendframework/zend-db/blob/master/LICENSE.md New BSD License
  */
 
+declare(strict_types=1);
+
 namespace Zend\Db\Sql\Ddl\Column;
 
 class Varchar extends AbstractLengthColumn
 {
-    /**
-     * @var string
-     */
+    /** @var string */
     protected $type = 'VARCHAR';
 }
diff --git a/src/Sql/Ddl/Constraint/AbstractConstraint.php b/src/Sql/Ddl/Constraint/AbstractConstraint.php
index d51f762cb5..e756825b68 100644
--- a/src/Sql/Ddl/Constraint/AbstractConstraint.php
+++ b/src/Sql/Ddl/Constraint/AbstractConstraint.php
@@ -1,46 +1,41 @@
 <?php
 /**
- * Zend Framework (http://framework.zend.com/)
- *
- * @link      http://github.com/zendframework/zf2 for the canonical source repository
- * @copyright Copyright (c) 2005-2016 Zend Technologies USA Inc. (http://www.zend.com)
- * @license   http://framework.zend.com/license/new-bsd New BSD License
+ * @see       https://github.com/zendframework/zend-db for the canonical source repository
+ * @copyright Copyright (c) 2005-2019 Zend Technologies USA Inc. (https://www.zend.com)
+ * @license   https://github.com/zendframework/zend-db/blob/master/LICENSE.md New BSD License
  */
 
+declare(strict_types=1);
+
 namespace Zend\Db\Sql\Ddl\Constraint;
 
+use function array_fill;
+use function array_merge;
+use function implode;
+use function sprintf;
+
 abstract class AbstractConstraint implements ConstraintInterface
 {
-    /**
-     * @var string
-     */
+    /** @var string */
     protected $columnSpecification = ' (%s)';
 
-    /**
-     * @var string
-     */
+    /** @var string */
     protected $namedSpecification = 'CONSTRAINT %s ';
 
-    /**
-     * @var string
-     */
+    /** @var string */
     protected $specification = '';
 
-    /**
-     * @var string
-     */
+    /** @var string */
     protected $name = '';
 
-    /**
-     * @var array
-     */
+    /** @var array */
     protected $columns = [];
 
     /**
      * @param null|string|array $columns
-     * @param null|string $name
+     * @param string            $name
      */
-    public function __construct($columns = null, $name = null)
+    public function __construct(?$columns = null, string $name = '')
     {
         if ($columns) {
             $this->setColumns($columns);
@@ -49,76 +44,61 @@ public function __construct($columns = null, $name = null)
         $this->setName($name);
     }
 
-    /**
-     * @param  string $name
-     * @return self Provides a fluent interface
-     */
-    public function setName($name)
+    public function setName(string $name) : self
     {
-        $this->name = (string) $name;
+        $this->name = $name;
+
         return $this;
     }
 
-    /**
-     * @return string
-     */
-    public function getName()
+    public function getName() : string
     {
         return $this->name;
     }
 
     /**
-     * @param  null|string|array $columns
-     * @return self Provides a fluent interface
+     * @param null|string|array $columns
+     * @return $this
      */
-    public function setColumns($columns)
+    public function setColumns($columns) : self
     {
         $this->columns = (array) $columns;
 
         return $this;
     }
 
-    /**
-     * @param  string $column
-     * @return self Provides a fluent interface
-     */
-    public function addColumn($column)
+    public function addColumn(string $column) : self
     {
         $this->columns[] = $column;
+
         return $this;
     }
 
-    /**
-     * {@inheritDoc}
-     */
-    public function getColumns()
+    public function getColumns() : array
     {
         return $this->columns;
     }
 
-    /**
-     * {@inheritDoc}
-     */
-    public function getExpressionData()
+    public function getExpressionData() : array
     {
-        $colCount = count($this->columns);
+        $colCount     = count($this->columns);
         $newSpecTypes = [];
-        $values = [];
-        $newSpec = '';
+        $values       = [];
+        $newSpec      = '';
 
         if ($this->name) {
-            $newSpec .= $this->namedSpecification;
-            $values[] = $this->name;
+            $newSpec       .= $this->namedSpecification;
+            $values[]       = $this->name;
             $newSpecTypes[] = self::TYPE_IDENTIFIER;
         }
 
         $newSpec .= $this->specification;
 
         if ($colCount) {
-            $values = array_merge($values, $this->columns);
+            $values       = array_merge($values, $this->columns);
             $newSpecParts = array_fill(0, $colCount, '%s');
             $newSpecTypes = array_merge($newSpecTypes, array_fill(0, $colCount, self::TYPE_IDENTIFIER));
-            $newSpec .= sprintf($this->columnSpecification, implode(', ', $newSpecParts));
+            $newSpec     .= sprintf($this->columnSpecification, implode(', ', $newSpecParts));
         }
 
         return [[
diff --git a/src/Sql/Ddl/Constraint/Check.php b/src/Sql/Ddl/Constraint/Check.php
index df3917b0e8..d8d0f2ca06 100644
--- a/src/Sql/Ddl/Constraint/Check.php
+++ b/src/Sql/Ddl/Constraint/Check.php
@@ -1,19 +1,21 @@
 <?php
 /**
- * Zend Framework (http://framework.zend.com/)
- *
- * @link      http://github.com/zendframework/zf2 for the canonical source repository
- * @copyright Copyright (c) 2005-2016 Zend Technologies USA Inc. (http://www.zend.com)
- * @license   http://framework.zend.com/license/new-bsd New BSD License
+ * @see       https://github.com/zendframework/zend-db for the canonical source repository
+ * @copyright Copyright (c) 2005-2019 Zend Technologies USA Inc. (https://www.zend.com)
+ * @license   https://github.com/zendframework/zend-db/blob/master/LICENSE.md New BSD License
  */
 
+declare(strict_types=1);
+
 namespace Zend\Db\Sql\Ddl\Constraint;
 
+use Zend\Db\Sql\ExpressionInterface;
+
+use function array_unshift;
+
 class Check extends AbstractConstraint
 {
-    /**
-     * @var string|\Zend\Db\Sql\ExpressionInterface
-     */
+    /** @var string|ExpressionInterface */
     protected $expression;
 
     /**
@@ -22,19 +24,16 @@ class Check extends AbstractConstraint
     protected $specification = 'CHECK (%s)';
 
     /**
-     * @param  string|\Zend\Db\Sql\ExpressionInterface $expression
-     * @param  null|string $name
+     * @param string|ExpressionInterface $expression
+     * @param string                     $name
      */
-    public function __construct($expression, $name)
+    public function __construct($expression, string $name = '')
     {
         $this->expression = $expression;
         $this->name       = $name;
     }
 
-    /**
-     * {@inheritDoc}
-     */
-    public function getExpressionData()
+    public function getExpressionData() : array
     {
         $newSpecTypes = [self::TYPE_LITERAL];
         $values       = [$this->expression];
diff --git a/src/Sql/Ddl/Constraint/ConstraintInterface.php b/src/Sql/Ddl/Constraint/ConstraintInterface.php
index aaa092022a..40c429d53a 100644
--- a/src/Sql/Ddl/Constraint/ConstraintInterface.php
+++ b/src/Sql/Ddl/Constraint/ConstraintInterface.php
@@ -1,12 +1,12 @@
 <?php
 /**
- * Zend Framework (http://framework.zend.com/)
- *
- * @link      http://github.com/zendframework/zf2 for the canonical source repository
- * @copyright Copyright (c) 2005-2016 Zend Technologies USA Inc. (http://www.zend.com)
- * @license   http://framework.zend.com/license/new-bsd New BSD License
+ * @see       https://github.com/zendframework/zend-db for the canonical source repository
+ * @copyright Copyright (c) 2005-2019 Zend Technologies USA Inc. (https://www.zend.com)
+ * @license   https://github.com/zendframework/zend-db/blob/master/LICENSE.md New BSD License
  */
 
+declare(strict_types=1);
+
 namespace Zend\Db\Sql\Ddl\Constraint;
 
 use Zend\Db\Sql\ExpressionInterface;
diff --git a/src/Sql/Ddl/Constraint/ForeignKey.php b/src/Sql/Ddl/Constraint/ForeignKey.php
index e834d3d9ee..203cbce3d5 100644
--- a/src/Sql/Ddl/Constraint/ForeignKey.php
+++ b/src/Sql/Ddl/Constraint/ForeignKey.php
@@ -1,34 +1,32 @@
 <?php
 /**
- * Zend Framework (http://framework.zend.com/)
- *
- * @link      http://github.com/zendframework/zf2 for the canonical source repository
- * @copyright Copyright (c) 2005-2016 Zend Technologies USA Inc. (http://www.zend.com)
- * @license   http://framework.zend.com/license/new-bsd New BSD License
+ * @see       https://github.com/zendframework/zend-db for the canonical source repository
+ * @copyright Copyright (c) 2005-2019 Zend Technologies USA Inc. (https://www.zend.com)
+ * @license   https://github.com/zendframework/zend-db/blob/master/LICENSE.md New BSD License
  */
 
+declare(strict_types=1);
+
 namespace Zend\Db\Sql\Ddl\Constraint;
 
+use function array_fill;
+use function array_merge;
+use function count;
+use function implode;
+use function sprintf;
+
 class ForeignKey extends AbstractConstraint
 {
-    /**
-     * @var string
-     */
+    /** @var string */
     protected $onDeleteRule = 'NO ACTION';
 
-    /**
-     * @var string
-     */
+    /** @var string */
     protected $onUpdateRule = 'NO ACTION';
 
-    /**
-     * @var string[]
-     */
+    /** @var string[] */
     protected $referenceColumn = [];
 
-    /**
-     * @var string
-     */
+    /** @var string */
     protected $referenceTable = '';
 
     /**
@@ -36,16 +34,14 @@ class ForeignKey extends AbstractConstraint
      */
     protected $columnSpecification = 'FOREIGN KEY (%s) ';
 
-    /**
-     * @var string[]
-     */
+    /** @var string[] */
     protected $referenceSpecification = [
         'REFERENCES %s ',
-        'ON DELETE %s ON UPDATE %s'
+        'ON DELETE %s ON UPDATE %s',
     ];
 
     /**
-     * @param null|string       $name
+     * @param string            $name
      * @param null|string|array $columns
      * @param string            $referenceTable
      * @param null|string|array $referenceColumn
@@ -53,12 +49,12 @@ class ForeignKey extends AbstractConstraint
      * @param null|string       $onUpdateRule
      */
     public function __construct(
-        $name,
+        string  $name,
         $columns,
-        $referenceTable,
+        string  $referenceTable,
         $referenceColumn,
-        $onDeleteRule = null,
-        $onUpdateRule = null
+        ?string $onDeleteRule = null,
+        ?string $onUpdateRule = null
     ) {
         $this->setName($name);
         $this->setColumns($columns);
@@ -74,85 +70,59 @@ public function __construct(
         }
     }
 
-    /**
-     * @param  string $referenceTable
-     * @return self Provides a fluent interface
-     */
-    public function setReferenceTable($referenceTable)
+    public function setReferenceTable(string $referenceTable) : self
     {
-        $this->referenceTable = (string) $referenceTable;
+        $this->referenceTable = $referenceTable;
+
         return $this;
     }
 
-    /**
-     * @return string
-     */
-    public function getReferenceTable()
+    public function getReferenceTable() : string
     {
         return $this->referenceTable;
     }
 
     /**
-     * @param  null|string|array $referenceColumn
-     * @return self Provides a fluent interface
+     * @param null|string|array $referenceColumn
+     * @return $this
      */
-    public function setReferenceColumn($referenceColumn)
+    public function setReferenceColumn($referenceColumn) : self
     {
         $this->referenceColumn = (array) $referenceColumn;
 
         return $this;
     }
 
-    /**
-     * @return array
-     */
-    public function getReferenceColumn()
+    public function getReferenceColumn() : array
     {
         return $this->referenceColumn;
     }
 
-    /**
-     * @param  string $onDeleteRule
-     * @return self Provides a fluent interface
-     */
-    public function setOnDeleteRule($onDeleteRule)
+    public function setOnDeleteRule(string $onDeleteRule) : self
     {
-        $this->onDeleteRule = (string) $onDeleteRule;
+        $this->onDeleteRule = $onDeleteRule;
 
         return $this;
     }
 
-    /**
-     * @return string
-     */
-    public function getOnDeleteRule()
+    public function getOnDeleteRule() : string
     {
         return $this->onDeleteRule;
     }
 
-    /**
-     * @param  string $onUpdateRule
-     * @return self Provides a fluent interface
-     */
-    public function setOnUpdateRule($onUpdateRule)
+    public function setOnUpdateRule(string $onUpdateRule) : self
     {
-        $this->onUpdateRule = (string) $onUpdateRule;
+        $this->onUpdateRule = $onUpdateRule;
 
         return $this;
     }
 
-    /**
-     * @return string
-     */
-    public function getOnUpdateRule()
+    public function getOnUpdateRule() : string
     {
         return $this->onUpdateRule;
     }
 
-    /**
-     * @return array
-     */
-    public function getExpressionData()
+    public function getExpressionData() : array
     {
         $data         = parent::getExpressionData();
         $colCount     = count($this->referenceColumn);
@@ -162,7 +132,8 @@ public function getExpressionData()
         $data[0][0] .= $this->referenceSpecification[0];
 
         if ($colCount) {
-            $values       = array_merge($values, $this->referenceColumn);
+            $values = array_merge($values, $this->referenceColumn);
+            
             $newSpecParts = array_fill(0, $colCount, '%s');
             $newSpecTypes = array_merge($newSpecTypes, array_fill(0, $colCount, self::TYPE_IDENTIFIER));
 
@@ -171,8 +142,9 @@ public function getExpressionData()
 
         $data[0][0] .= $this->referenceSpecification[1];
 
-        $values[]       = $this->onDeleteRule;
-        $values[]       = $this->onUpdateRule;
+        $values[] = $this->onDeleteRule;
+        $values[] = $this->onUpdateRule;
+
         $newSpecTypes[] = self::TYPE_LITERAL;
         $newSpecTypes[] = self::TYPE_LITERAL;
 
diff --git a/src/Sql/Ddl/Constraint/PrimaryKey.php b/src/Sql/Ddl/Constraint/PrimaryKey.php
index 9775bb018f..07f781d789 100644
--- a/src/Sql/Ddl/Constraint/PrimaryKey.php
+++ b/src/Sql/Ddl/Constraint/PrimaryKey.php
@@ -1,18 +1,16 @@
 <?php
 /**
- * Zend Framework (http://framework.zend.com/)
- *
- * @link      http://github.com/zendframework/zf2 for the canonical source repository
- * @copyright Copyright (c) 2005-2016 Zend Technologies USA Inc. (http://www.zend.com)
- * @license   http://framework.zend.com/license/new-bsd New BSD License
+ * @see       https://github.com/zendframework/zend-db for the canonical source repository
+ * @copyright Copyright (c) 2005-2019 Zend Technologies USA Inc. (https://www.zend.com)
+ * @license   https://github.com/zendframework/zend-db/blob/master/LICENSE.md New BSD License
  */
 
+declare(strict_types=1);
+
 namespace Zend\Db\Sql\Ddl\Constraint;
 
 class PrimaryKey extends AbstractConstraint
 {
-    /**
-     * @var string
-     */
+    /** @var string */
     protected $specification = 'PRIMARY KEY';
 }
diff --git a/src/Sql/Ddl/Constraint/UniqueKey.php b/src/Sql/Ddl/Constraint/UniqueKey.php
index b46dbd159b..f078f05f3f 100644
--- a/src/Sql/Ddl/Constraint/UniqueKey.php
+++ b/src/Sql/Ddl/Constraint/UniqueKey.php
@@ -1,18 +1,16 @@
 <?php
 /**
- * Zend Framework (http://framework.zend.com/)
- *
- * @link      http://github.com/zendframework/zf2 for the canonical source repository
- * @copyright Copyright (c) 2005-2016 Zend Technologies USA Inc. (http://www.zend.com)
- * @license   http://framework.zend.com/license/new-bsd New BSD License
+ * @see       https://github.com/zendframework/zend-db for the canonical source repository
+ * @copyright Copyright (c) 2005-2019 Zend Technologies USA Inc. (https://www.zend.com)
+ * @license   https://github.com/zendframework/zend-db/blob/master/LICENSE.md New BSD License
  */
 
+declare(strict_types=1);
+
 namespace Zend\Db\Sql\Ddl\Constraint;
 
 class UniqueKey extends AbstractConstraint
 {
-    /**
-     * @var string
-     */
+    /** @var string */
     protected $specification = 'UNIQUE';
 }
diff --git a/src/Sql/Ddl/CreateTable.php b/src/Sql/Ddl/CreateTable.php
index ce135e019e..46e50d54e4 100644
--- a/src/Sql/Ddl/CreateTable.php
+++ b/src/Sql/Ddl/CreateTable.php
@@ -1,126 +1,99 @@
 <?php
 /**
- * Zend Framework (http://framework.zend.com/)
- *
- * @link      http://github.com/zendframework/zf2 for the canonical source repository
- * @copyright Copyright (c) 2005-2016 Zend Technologies USA Inc. (http://www.zend.com)
- * @license   http://framework.zend.com/license/new-bsd New BSD License
+ * @see       https://github.com/zendframework/zend-db for the canonical source repository
+ * @copyright Copyright (c) 2005-2019 Zend Technologies USA Inc. (https://www.zend.com)
+ * @license   https://github.com/zendframework/zend-db/blob/master/LICENSE.md New BSD License
  */
 
+declare(strict_types=1);
+
 namespace Zend\Db\Sql\Ddl;
 
 use Zend\Db\Adapter\Platform\PlatformInterface;
 use Zend\Db\Sql\AbstractSql;
+use Zend\Db\Sql\Ddl\Column\ColumnInterface;
+use Zend\Db\Sql\Ddl\Constraint\ConstraintInterface;
 use Zend\Db\Sql\TableIdentifier;
+use function array_key_exists;
 
 class CreateTable extends AbstractSql implements SqlInterface
 {
-    const COLUMNS     = 'columns';
-    const CONSTRAINTS = 'constraints';
-    const TABLE       = 'table';
+    public const COLUMNS     = 'columns';
+    public const CONSTRAINTS = 'constraints';
+    public const TABLE       = 'table';
 
-    /**
-     * @var Column\ColumnInterface[]
-     */
+    /** @var Column\ColumnInterface[] */
     protected $columns = [];
 
-    /**
-     * @var string[]
-     */
+    /** @var string[] */
     protected $constraints = [];
 
-    /**
-     * @var bool
-     */
+    /** @var bool */
     protected $isTemporary = false;
 
-    /**
-     * {@inheritDoc}
-     */
     protected $specifications = [
         self::TABLE => 'CREATE %1$sTABLE %2$s (',
         self::COLUMNS  => [
             "\n    %1\$s" => [
-                [1 => '%1$s', 'combinedby' => ",\n    "]
-            ]
+                [1 => '%1$s', 'combinedby' => ",\n    "],
+            ],
         ],
-        'combinedBy' => ",",
+        'combinedBy' => ',',
         self::CONSTRAINTS => [
             "\n    %1\$s" => [
-                [1 => '%1$s', 'combinedby' => ",\n    "]
-            ]
+                [1 => '%1$s', 'combinedby' => ",\n    "],
+            ],
         ],
         'statementEnd' => '%1$s',
     ];
 
-    /**
-     * @var string
-     */
+    /** @var string */
     protected $table = '';
 
     /**
      * @param string|TableIdentifier $table
-     * @param bool   $isTemporary
+     * @param bool                   $isTemporary
      */
-    public function __construct($table = '', $isTemporary = false)
+    public function __construct($table = '', bool $isTemporary = false)
     {
         $this->table = $table;
         $this->setTemporary($isTemporary);
     }
 
-    /**
-     * @param  bool $temporary
-     * @return self Provides a fluent interface
-     */
-    public function setTemporary($temporary)
+    public function setTemporary(bool $temporary) : self
     {
-        $this->isTemporary = (bool) $temporary;
+        $this->isTemporary = $temporary;
+
         return $this;
     }
 
-    /**
-     * @return bool
-     */
-    public function isTemporary()
+    public function isTemporary() : bool
     {
         return $this->isTemporary;
     }
 
-    /**
-     * @param  string $name
-     * @return self Provides a fluent interface
-     */
-    public function setTable($name)
+    public function setTable(string $name) : self
     {
         $this->table = $name;
+
         return $this;
     }
 
-    /**
-     * @param  Column\ColumnInterface $column
-     * @return self Provides a fluent interface
-     */
-    public function addColumn(Column\ColumnInterface $column)
+    public function addColumn(ColumnInterface $column) : self
     {
         $this->columns[] = $column;
+
         return $this;
     }
 
-    /**
-     * @param  Constraint\ConstraintInterface $constraint
-     * @return self Provides a fluent interface
-     */
-    public function addConstraint(Constraint\ConstraintInterface $constraint)
+    public function addConstraint(ConstraintInterface $constraint) : self
     {
         $this->constraints[] = $constraint;
+
         return $this;
     }
 
-    /**
-     * @param  string|null $key
-     * @return array
-     */
-    public function getRawState($key = null)
+    public function getRawState(?string $key = null) : array
     {
         $rawState = [
             self::COLUMNS     => $this->columns,
@@ -131,12 +104,7 @@ public function getRawState($key = null)
         return (isset($key) && array_key_exists($key, $rawState)) ? $rawState[$key] : $rawState;
     }
 
-    /**
-     * @param PlatformInterface $adapterPlatform
-     *
-     * @return string[]
-     */
-    protected function processTable(PlatformInterface $adapterPlatform = null)
+    protected function processTable(?PlatformInterface $adapterPlatform = null) : array
     {
         return [
             $this->isTemporary ? 'TEMPORARY ' : '',
@@ -146,10 +114,9 @@ protected function processTable(PlatformInterface $adapterPlatform = null)
 
     /**
      * @param PlatformInterface $adapterPlatform
-     *
      * @return string[][]|null
      */
-    protected function processColumns(PlatformInterface $adapterPlatform = null)
+    protected function processColumns(?PlatformInterface $adapterPlatform = null)
     {
         if (! $this->columns) {
             return;
@@ -165,11 +132,10 @@ protected function processColumns(PlatformInterface $adapterPlatform = null)
     }
 
     /**
-     * @param PlatformInterface $adapterPlatform
-     *
-     * @return array|string
+     * @param PlatformInterface|null $adapterPlatform
+     * @return array|string|null
      */
-    protected function processCombinedby(PlatformInterface $adapterPlatform = null)
+    protected function processCombinedby(?PlatformInterface $adapterPlatform = null)
     {
         if ($this->constraints && $this->columns) {
             return $this->specifications['combinedBy'];
@@ -177,11 +143,10 @@ protected function processCombinedby(PlatformInterface $adapterPlatform = null)
     }
 
     /**
-     * @param PlatformInterface $adapterPlatform
-     *
+     * @param PlatformInterface|null $adapterPlatform
      * @return string[][]|null
      */
-    protected function processConstraints(PlatformInterface $adapterPlatform = null)
+    protected function processConstraints(?PlatformInterface $adapterPlatform = null)
     {
         if (! $this->constraints) {
             return;
@@ -196,12 +161,7 @@ protected function processConstraints(PlatformInterface $adapterPlatform = null)
         return [$sqls];
     }
 
-    /**
-     * @param PlatformInterface $adapterPlatform
-     *
-     * @return string[]
-     */
-    protected function processStatementEnd(PlatformInterface $adapterPlatform = null)
+    protected function processStatementEnd(?PlatformInterface $adapterPlatform = null) : array
     {
         return ["\n)"];
     }
diff --git a/src/Sql/Ddl/DropTable.php b/src/Sql/Ddl/DropTable.php
index c42f8399cb..d7025f34fb 100644
--- a/src/Sql/Ddl/DropTable.php
+++ b/src/Sql/Ddl/DropTable.php
@@ -1,12 +1,12 @@
 <?php
 /**
- * Zend Framework (http://framework.zend.com/)
- *
- * @link      http://github.com/zendframework/zf2 for the canonical source repository
- * @copyright Copyright (c) 2005-2016 Zend Technologies USA Inc. (http://www.zend.com)
- * @license   http://framework.zend.com/license/new-bsd New BSD License
+ * @see       https://github.com/zendframework/zend-db for the canonical source repository
+ * @copyright Copyright (c) 2005-2019 Zend Technologies USA Inc. (https://www.zend.com)
+ * @license   https://github.com/zendframework/zend-db/blob/master/LICENSE.md New BSD License
  */
 
+declare(strict_types=1);
+
 namespace Zend\Db\Sql\Ddl;
 
 use Zend\Db\Adapter\Platform\PlatformInterface;
@@ -15,18 +15,14 @@
 
 class DropTable extends AbstractSql implements SqlInterface
 {
-    const TABLE = 'table';
+    public const TABLE = 'table';
 
-    /**
-     * @var array
-     */
+    /** @var array */
     protected $specifications = [
-        self::TABLE => 'DROP TABLE %1$s'
+        self::TABLE => 'DROP TABLE %1$s',
     ];
 
-    /**
-     * @var string
-     */
+    /** @var string */
     protected $table = '';
 
     /**
@@ -37,7 +33,7 @@ public function __construct($table = '')
         $this->table = $table;
     }
 
-    protected function processTable(PlatformInterface $adapterPlatform = null)
+    protected function processTable(?PlatformInterface $adapterPlatform = null) : array
     {
         return [$this->resolveTable($this->table, $adapterPlatform)];
     }
diff --git a/src/Sql/Ddl/Index/AbstractIndex.php b/src/Sql/Ddl/Index/AbstractIndex.php
index c11efb5d5b..8f7cfa9489 100644
--- a/src/Sql/Ddl/Index/AbstractIndex.php
+++ b/src/Sql/Ddl/Index/AbstractIndex.php
@@ -1,12 +1,12 @@
 <?php
 /**
- * Zend Framework (http://framework.zend.com/)
- *
- * @link      http://github.com/zendframework/zf2 for the canonical source repository
- * @copyright Copyright (c) 2005-2016 Zend Technologies USA Inc. (http://www.zend.com)
- * @license   http://framework.zend.com/license/new-bsd New BSD License
+ * @see       https://github.com/zendframework/zend-db for the canonical source repository
+ * @copyright Copyright (c) 2005-2019 Zend Technologies USA Inc. (https://www.zend.com)
+ * @license   https://github.com/zendframework/zend-db/blob/master/LICENSE.md New BSD License
  */
 
+declare(strict_types=1);
+
 namespace Zend\Db\Sql\Ddl\Index;
 
 use Zend\Db\Sql\Ddl\Constraint\AbstractConstraint;
diff --git a/src/Sql/Ddl/Index/Index.php b/src/Sql/Ddl/Index/Index.php
index a0239089a4..88ffa48f52 100644
--- a/src/Sql/Ddl/Index/Index.php
+++ b/src/Sql/Ddl/Index/Index.php
@@ -1,41 +1,41 @@
 <?php
 /**
- * Zend Framework (http://framework.zend.com/)
- *
- * @link      http://github.com/zendframework/zf2 for the canonical source repository
- * @copyright Copyright (c) 2005-2016 Zend Technologies USA Inc. (http://www.zend.com)
- * @license   http://framework.zend.com/license/new-bsd New BSD License
+ * @see       https://github.com/zendframework/zend-db for the canonical source repository
+ * @copyright Copyright (c) 2005-2019 Zend Technologies USA Inc. (https://www.zend.com)
+ * @license   https://github.com/zendframework/zend-db/blob/master/LICENSE.md New BSD License
  */
 
+declare(strict_types=1);
+
 namespace Zend\Db\Sql\Ddl\Index;
 
+use function array_merge;
+use function count;
+use function implode;
+use function str_replace;
+
 class Index extends AbstractIndex
 {
-    /**
-     * @var string
-     */
+    /** @var string */
     protected $specification = 'INDEX %s(...)';
 
-    /**
-     * @var array
-     */
+    /** @var array */
     protected $lengths;
 
     /**
-     * @param  string|array|null $columns
-     * @param  null|string $name
-     * @param array $lengths
+     * @param string|array|null $columns
+     * @param string            $name
+     * @param array             $lengths
      */
-    public function __construct($columns, $name = null, array $lengths = [])
+    public function __construct($columns, string $name = '', array $lengths = [])
     {
         $this->setColumns($columns);
+        $this->setName($name);
 
-        $this->name    = null === $name ? null : (string) $name;
         $this->lengths = $lengths;
     }
 
     /**
-     *
      * @return array of array|string should return an array in the format:
      *
      * array (
@@ -50,11 +50,11 @@ public function __construct($columns, $name = null, array $lengths = [])
      * )
      *
      */
-    public function getExpressionData()
+    public function getExpressionData() : array
     {
         $colCount     = count($this->columns);
         $values       = [];
-        $values[]     = $this->name ?: '';
+        $values[]     = $this->name ?? '';
         $newSpecTypes = [self::TYPE_IDENTIFIER];
         $newSpecParts = [];
 
diff --git a/src/Sql/Ddl/SqlInterface.php b/src/Sql/Ddl/SqlInterface.php
index 0f8660f452..519a9690fa 100644
--- a/src/Sql/Ddl/SqlInterface.php
+++ b/src/Sql/Ddl/SqlInterface.php
@@ -1,12 +1,12 @@
 <?php
 /**
- * Zend Framework (http://framework.zend.com/)
- *
- * @link      http://github.com/zendframework/zf2 for the canonical source repository
- * @copyright Copyright (c) 2005-2016 Zend Technologies USA Inc. (http://www.zend.com)
- * @license   http://framework.zend.com/license/new-bsd New BSD License
+ * @see       https://github.com/zendframework/zend-db for the canonical source repository
+ * @copyright Copyright (c) 2005-2019 Zend Technologies USA Inc. (https://www.zend.com)
+ * @license   https://github.com/zendframework/zend-db/blob/master/LICENSE.md New BSD License
  */
 
+declare(strict_types=1);
+
 namespace Zend\Db\Sql\Ddl;
 
 use Zend\Db\Sql\SqlInterface as BaseSqlInterface;
diff --git a/src/Sql/Delete.php b/src/Sql/Delete.php
index 9e70e5fcd3..93d5755188 100644
--- a/src/Sql/Delete.php
+++ b/src/Sql/Delete.php
@@ -1,20 +1,23 @@
 <?php
 /**
- * Zend Framework (http://framework.zend.com/)
- *
- * @link      http://github.com/zendframework/zf2 for the canonical source repository
- * @copyright Copyright (c) 2005-2016 Zend Technologies USA Inc. (http://www.zend.com)
- * @license   http://framework.zend.com/license/new-bsd New BSD License
+ * @see       https://github.com/zendframework/zend-db for the canonical source repository
+ * @copyright Copyright (c) 2005-2019 Zend Technologies USA Inc. (https://www.zend.com)
+ * @license   https://github.com/zendframework/zend-db/blob/master/LICENSE.md New BSD License
  */
 
+declare(strict_types=1);
+
 namespace Zend\Db\Sql;
 
+use Zend\Db\Adapter\Driver\DriverInterface;
 use Zend\Db\Adapter\ParameterContainer;
 use Zend\Db\Adapter\Platform\PlatformInterface;
-use Zend\Db\Adapter\Driver\DriverInterface;
+use Zend\Db\Sql\Predicate\PredicateSet;
+use function array_key_exists;
+use function sprintf;
+use function strtolower;
 
 /**
- *
  * @property Where $where
  */
 class Delete extends AbstractPreparableSql
@@ -22,8 +25,8 @@ class Delete extends AbstractPreparableSql
     /**@#+
      * @const
      */
-    const SPECIFICATION_DELETE = 'delete';
-    const SPECIFICATION_WHERE = 'where';
+    public const SPECIFICATION_DELETE = 'delete';
+    public const SPECIFICATION_WHERE  = 'where';
     /**@#-*/
 
     /**
@@ -31,79 +34,68 @@ class Delete extends AbstractPreparableSql
      */
     protected $specifications = [
         self::SPECIFICATION_DELETE => 'DELETE FROM %1$s',
-        self::SPECIFICATION_WHERE => 'WHERE %1$s'
+        self::SPECIFICATION_WHERE  => 'WHERE %1$s',
     ];
 
-    /**
-     * @var string|TableIdentifier
-     */
+    /** @var string|TableIdentifier */
     protected $table = '';
 
-    /**
-     * @var bool
-     */
+    /** @var bool */
     protected $emptyWhereProtection = true;
 
-    /**
-     * @var array
-     */
+    /** @var array */
     protected $set = [];
 
-    /**
-     * @var null|string|Where
-     */
-    protected $where = null;
+    /** @var null|string|Where */
+    protected $where;
 
     /**
      * Constructor
      *
-     * @param  null|string|TableIdentifier $table
+     * @param null|string|TableIdentifier $table
      */
     public function __construct($table = null)
     {
         if ($table) {
             $this->from($table);
         }
+
         $this->where = new Where();
     }
 
     /**
      * Create from statement
      *
-     * @param  string|TableIdentifier $table
-     * @return self Provides a fluent interface
+     * @param string|TableIdentifier $table
+     * @return $this
      */
-    public function from($table)
+    public function from($table) : self
     {
         $this->table = $table;
+
         return $this;
     }
 
-    /**
-     * @param null $key
-     *
-     * @return mixed
-     */
-    public function getRawState($key = null)
+    public function getRawState(?string $key = null)
     {
         $rawState = [
             'emptyWhereProtection' => $this->emptyWhereProtection,
-            'table' => $this->table,
-            'set' => $this->set,
-            'where' => $this->where
+            'table'                => $this->table,
+            'set'                  => $this->set,
+            'where'                => $this->where,
         ];
+
         return (isset($key) && array_key_exists($key, $rawState)) ? $rawState[$key] : $rawState;
     }
 
     /**
      * Create where clause
      *
-     * @param  Where|\Closure|string|array $predicate
-     * @param  string $combination One of the OP_* constants from Predicate\PredicateSet
-     *
-     * @return self Provides a fluent interface
+     * @param Where|\Closure|string|array $predicate
+     * @param string $combination One of the OP_* constants from Predicate\PredicateSet
+     * @return $this
      */
-    public function where($predicate, $combination = Predicate\PredicateSet::OP_AND)
+    public function where($predicate, string $combination = PredicateSet::OP_AND) : self
     {
         if ($predicate instanceof Where) {
             $this->where = $predicate;
@@ -113,60 +105,36 @@ public function where($predicate, $combination = Predicate\PredicateSet::OP_AND)
         return $this;
     }
 
-    /**
-     * @param PlatformInterface       $platform
-     * @param DriverInterface|null    $driver
-     * @param ParameterContainer|null $parameterContainer
-     *
-     * @return string
-     */
     protected function processDelete(
-        PlatformInterface $platform,
-        DriverInterface $driver = null,
-        ParameterContainer $parameterContainer = null
-    ) {
+        PlatformInterface   $platform,
+        ?DriverInterface    $driver = null,
+        ?ParameterContainer $parameterContainer = null
+    ) : string {
         return sprintf(
             $this->specifications[static::SPECIFICATION_DELETE],
             $this->resolveTable($this->table, $platform, $driver, $parameterContainer)
         );
     }
 
-    /**
-     * @param PlatformInterface       $platform
-     * @param DriverInterface|null    $driver
-     * @param ParameterContainer|null $parameterContainer
-     *
-     * @return null|string
-     */
     protected function processWhere(
-        PlatformInterface $platform,
-        DriverInterface $driver = null,
-        ParameterContainer $parameterContainer = null
-    ) {
-        if ($this->where->count() == 0) {
-            return;
+        PlatformInterface   $platform,
+        ?DriverInterface    $driver = null,
+        ?ParameterContainer $parameterContainer = null
+    ) : ?string {
+        if ($this->where->count() === 0) {
+            return null;
         }
 
         return sprintf(
             $this->specifications[static::SPECIFICATION_WHERE],
-            $this->processExpression($this->where, $platform, $driver, $parameterContainer, 'where')
+            $this->processExpression($this->where, $platform, $driver, $parameterContainer, self::SPECIFICATION_WHERE)
         );
     }
 
-    /**
-     * Property overloading
-     *
-     * Overloads "where" only.
-     *
-     * @param  string $name
-     *
-     * @return Where|null
-     */
-    public function __get($name)
+    public function __get(string $name) : ?Where
     {
-        switch (strtolower($name)) {
-            case 'where':
-                return $this->where;
+        if (strtolower($name) === self::SPECIFICATION_WHERE) {
+            return $this->where;
         }
     }
 }
diff --git a/src/Sql/Exception/ExceptionInterface.php b/src/Sql/Exception/ExceptionInterface.php
index 138f7e4d62..d29824c57f 100644
--- a/src/Sql/Exception/ExceptionInterface.php
+++ b/src/Sql/Exception/ExceptionInterface.php
@@ -1,12 +1,12 @@
 <?php
 /**
- * Zend Framework (http://framework.zend.com/)
- *
- * @link      http://github.com/zendframework/zf2 for the canonical source repository
- * @copyright Copyright (c) 2005-2016 Zend Technologies USA Inc. (http://www.zend.com)
- * @license   http://framework.zend.com/license/new-bsd New BSD License
+ * @see       https://github.com/zendframework/zend-db for the canonical source repository
+ * @copyright Copyright (c) 2005-2019 Zend Technologies USA Inc. (https://www.zend.com)
+ * @license   https://github.com/zendframework/zend-db/blob/master/LICENSE.md New BSD License
  */
 
+declare(strict_types=1);
+
 namespace Zend\Db\Sql\Exception;
 
 use Zend\Db\Exception;
diff --git a/src/Sql/Exception/InvalidArgumentException.php b/src/Sql/Exception/InvalidArgumentException.php
index 6e400031d4..ed70a96ad1 100644
--- a/src/Sql/Exception/InvalidArgumentException.php
+++ b/src/Sql/Exception/InvalidArgumentException.php
@@ -1,12 +1,12 @@
 <?php
 /**
- * Zend Framework (http://framework.zend.com/)
- *
- * @link      http://github.com/zendframework/zf2 for the canonical source repository
- * @copyright Copyright (c) 2005-2016 Zend Technologies USA Inc. (http://www.zend.com)
- * @license   http://framework.zend.com/license/new-bsd New BSD License
+ * @see       https://github.com/zendframework/zend-db for the canonical source repository
+ * @copyright Copyright (c) 2005-2019 Zend Technologies USA Inc. (https://www.zend.com)
+ * @license   https://github.com/zendframework/zend-db/blob/master/LICENSE.md New BSD License
  */
 
+declare(strict_types=1);
+
 namespace Zend\Db\Sql\Exception;
 
 use Zend\Db\Exception;
diff --git a/src/Sql/Exception/RuntimeException.php b/src/Sql/Exception/RuntimeException.php
index 82b3aab91f..1d369b8ec7 100644
--- a/src/Sql/Exception/RuntimeException.php
+++ b/src/Sql/Exception/RuntimeException.php
@@ -1,12 +1,12 @@
 <?php
 /**
- * Zend Framework (http://framework.zend.com/)
- *
- * @link      http://github.com/zendframework/zf2 for the canonical source repository
- * @copyright Copyright (c) 2005-2016 Zend Technologies USA Inc. (http://www.zend.com)
- * @license   http://framework.zend.com/license/new-bsd New BSD License
+ * @see       https://github.com/zendframework/zend-db for the canonical source repository
+ * @copyright Copyright (c) 2005-2019 Zend Technologies USA Inc. (https://www.zend.com)
+ * @license   https://github.com/zendframework/zend-db/blob/master/LICENSE.md New BSD License
  */
 
+declare(strict_types=1);
+
 namespace Zend\Db\Sql\Exception;
 
 use Zend\Db\Exception;
diff --git a/src/Sql/Expression.php b/src/Sql/Expression.php
index 496cda92a8..24932b730b 100644
--- a/src/Sql/Expression.php
+++ b/src/Sql/Expression.php
@@ -1,42 +1,44 @@
 <?php
 /**
- * Zend Framework (http://framework.zend.com/)
- *
- * @link      http://github.com/zendframework/zf2 for the canonical source repository
- * @copyright Copyright (c) 2005-2016 Zend Technologies USA Inc. (http://www.zend.com)
- * @license   http://framework.zend.com/license/new-bsd New BSD License
+ * @see       https://github.com/zendframework/zend-db for the canonical source repository
+ * @copyright Copyright (c) 2005-2019 Zend Technologies USA Inc. (https://www.zend.com)
+ * @license   https://github.com/zendframework/zend-db/blob/master/LICENSE.md New BSD License
  */
 
+declare(strict_types=1);
+
 namespace Zend\Db\Sql;
 
+use function count;
+use function is_array;
+use function is_scalar;
+use function is_string;
+use function preg_match_all;
+use function str_ireplace;
+use function str_replace;
+
 class Expression extends AbstractExpression
 {
     /**
      * @const
      */
-    const PLACEHOLDER = '?';
+    public const PLACEHOLDER = '?';
 
-    /**
-     * @var string
-     */
+    /** @var string */
     protected $expression = '';
 
-    /**
-     * @var array
-     */
+    /** @var array */
     protected $parameters = [];
 
-    /**
-     * @var array
-     */
+    /** @var array */
     protected $types = [];
 
     /**
-     * @param string $expression
-     * @param string|array $parameters
-     * @param array $types @deprecated will be dropped in version 3.0.0
+     * @param string            $expression
+     * @param null|string|array $parameters
+     * @param array             $types @deprecated will be dropped in version 3.0.0
      */
-    public function __construct($expression = '', $parameters = null, array $types = [])
+    public function __construct(string $expression = '', $parameters = null, array $types = [])
     {
         if ($expression !== '') {
             $this->setExpression($expression);
@@ -61,46 +63,39 @@ public function __construct($expression = '', $parameters = null, array $types =
         }
     }
 
-    /**
-     * @param $expression
-     * @return self Provides a fluent interface
-     * @throws Exception\InvalidArgumentException
-     */
-    public function setExpression($expression)
+    public function setExpression(string $expression) : self
     {
-        if (! is_string($expression) || $expression == '') {
+        if (! is_string($expression) || $expression === '') {
             throw new Exception\InvalidArgumentException('Supplied expression must be a string.');
         }
+
         $this->expression = $expression;
+
         return $this;
     }
 
-    /**
-     * @return string
-     */
-    public function getExpression()
+    public function getExpression() : string
     {
         return $this->expression;
     }
 
     /**
      * @param $parameters
-     * @return self Provides a fluent interface
+     * @return $this
      * @throws Exception\InvalidArgumentException
      */
-    public function setParameters($parameters)
+    public function setParameters($parameters) : self
     {
         if (! is_scalar($parameters) && ! is_array($parameters)) {
             throw new Exception\InvalidArgumentException('Expression parameters must be a scalar or array.');
         }
+
         $this->parameters = $parameters;
+
         return $this;
     }
 
-    /**
-     * @return array
-     */
-    public function getParameters()
+    public function getParameters() : array
     {
         return $this->parameters;
     }
@@ -108,11 +103,12 @@ public function getParameters()
     /**
      * @deprecated
      * @param array $types
-     * @return self Provides a fluent interface
+     * @return $this
      */
-    public function setTypes(array $types)
+    public function setTypes(array $types) : self
     {
         $this->types = $types;
+
         return $this;
     }
 
@@ -120,22 +116,18 @@ public function setTypes(array $types)
      * @deprecated
      * @return array
      */
-    public function getTypes()
+    public function getTypes() : array
     {
         return $this->types;
     }
 
-    /**
-     * @return array
-     * @throws Exception\RuntimeException
-     */
-    public function getExpressionData()
+    public function getExpressionData() : array
     {
-        $parameters = (is_scalar($this->parameters)) ? [$this->parameters] : $this->parameters;
+        $parameters      = is_scalar($this->parameters) ? [$this->parameters] : $this->parameters;
         $parametersCount = count($parameters);
-        $expression = str_replace('%', '%%', $this->expression);
+        $expression      = str_replace('%', '%%', $this->expression);
 
-        if ($parametersCount == 0) {
+        if ($parametersCount === 0) {
             return [
                 str_ireplace(self::PLACEHOLDER, '', $expression)
             ];
@@ -155,10 +147,11 @@ public function getExpressionData()
         foreach ($parameters as $parameter) {
             list($values[], $types[]) = $this->normalizeArgument($parameter, self::TYPE_VALUE);
         }
+
         return [[
             $expression,
             $values,
-            $types
+            $types,
         ]];
     }
 }
diff --git a/src/Sql/ExpressionInterface.php b/src/Sql/ExpressionInterface.php
index 282b408683..1d19164338 100644
--- a/src/Sql/ExpressionInterface.php
+++ b/src/Sql/ExpressionInterface.php
@@ -1,24 +1,23 @@
 <?php
 /**
- * Zend Framework (http://framework.zend.com/)
- *
- * @link      http://github.com/zendframework/zf2 for the canonical source repository
- * @copyright Copyright (c) 2005-2016 Zend Technologies USA Inc. (http://www.zend.com)
- * @license   http://framework.zend.com/license/new-bsd New BSD License
+ * @see       https://github.com/zendframework/zend-db for the canonical source repository
+ * @copyright Copyright (c) 2005-2019 Zend Technologies USA Inc. (https://www.zend.com)
+ * @license   https://github.com/zendframework/zend-db/blob/master/LICENSE.md New BSD License
  */
 
+declare(strict_types=1);
+
 namespace Zend\Db\Sql;
 
 interface ExpressionInterface
 {
-    const TYPE_IDENTIFIER = 'identifier';
-    const TYPE_VALUE = 'value';
-    const TYPE_LITERAL = 'literal';
-    const TYPE_SELECT = 'select';
+    public const TYPE_IDENTIFIER = 'identifier';
+    public const TYPE_VALUE      = 'value';
+    public const TYPE_LITERAL    = 'literal';
+    public const TYPE_SELECT     = 'select';
 
     /**
      * @abstract
-     *
      * @return array of array|string should return an array in the format:
      *
      * array (
@@ -33,5 +32,5 @@ interface ExpressionInterface
      * )
      *
      */
-    public function getExpressionData();
+    public function getExpressionData() : array;
 }
diff --git a/src/Sql/Having.php b/src/Sql/Having.php
index b95d9d5910..9e93288e3b 100644
--- a/src/Sql/Having.php
+++ b/src/Sql/Having.php
@@ -1,12 +1,12 @@
 <?php
 /**
- * Zend Framework (http://framework.zend.com/)
- *
- * @link      http://github.com/zendframework/zf2 for the canonical source repository
- * @copyright Copyright (c) 2005-2016 Zend Technologies USA Inc. (http://www.zend.com)
- * @license   http://framework.zend.com/license/new-bsd New BSD License
+ * @see       https://github.com/zendframework/zend-db for the canonical source repository
+ * @copyright Copyright (c) 2005-2019 Zend Technologies USA Inc. (https://www.zend.com)
+ * @license   https://github.com/zendframework/zend-db/blob/master/LICENSE.md New BSD License
  */
 
+declare(strict_types=1);
+
 namespace Zend\Db\Sql;
 
 class Having extends Predicate\Predicate
diff --git a/src/Sql/Insert.php b/src/Sql/Insert.php
index ad5ce89981..0e784bc071 100644
--- a/src/Sql/Insert.php
+++ b/src/Sql/Insert.php
@@ -1,18 +1,28 @@
 <?php
 /**
- * Zend Framework (http://framework.zend.com/)
- *
- * @link      http://github.com/zendframework/zf2 for the canonical source repository
- * @copyright Copyright (c) 2005-2016 Zend Technologies USA Inc. (http://www.zend.com)
- * @license   http://framework.zend.com/license/new-bsd New BSD License
+ * @see       https://github.com/zendframework/zend-db for the canonical source repository
+ * @copyright Copyright (c) 2005-2019 Zend Technologies USA Inc. (https://www.zend.com)
+ * @license   https://github.com/zendframework/zend-db/blob/master/LICENSE.md New BSD License
  */
 
+declare(strict_types=1);
+
 namespace Zend\Db\Sql;
 
 use Zend\Db\Adapter\Driver\DriverInterface;
 use Zend\Db\Adapter\Driver\Pdo\Pdo;
 use Zend\Db\Adapter\ParameterContainer;
 use Zend\Db\Adapter\Platform\PlatformInterface;
+use function array_combine;
+use function array_flip;
+use function array_key_exists;
+use function array_keys;
+use function array_values;
+use function count;
+use function implode;
+use function is_array;
+use function is_scalar;
+use function range;
 
 class Insert extends AbstractPreparableSql
 {
@@ -21,35 +31,29 @@ class Insert extends AbstractPreparableSql
      *
      * @const
      */
-    const SPECIFICATION_INSERT = 'insert';
-    const SPECIFICATION_SELECT = 'select';
-    const VALUES_MERGE = 'merge';
-    const VALUES_SET   = 'set';
+    public const SPECIFICATION_INSERT = 'insert';
+    public const SPECIFICATION_SELECT = 'select';
+    public const VALUES_MERGE         = 'merge';
+    public const VALUES_SET           = 'set';
     /**#@-*/
 
-    /**
-     * @var array Specification array
-     */
+    /** @var array Specification array */
     protected $specifications = [
         self::SPECIFICATION_INSERT => 'INSERT INTO %1$s (%2$s) VALUES (%3$s)',
         self::SPECIFICATION_SELECT => 'INSERT INTO %1$s %2$s %3$s',
     ];
 
-    /**
-     * @var string|TableIdentifier
-     */
-    protected $table            = null;
-    protected $columns          = [];
+    /** @var string|TableIdentifier */
+    protected $table;
+    protected $columns = [];
 
-    /**
-     * @var array|Select
-     */
-    protected $select           = null;
+    /** @var array|Select */
+    protected $select;
 
     /**
      * Constructor
      *
-     * @param  null|string|TableIdentifier $table
+     * @param null|string|TableIdentifier $table
      */
     public function __construct($table = null)
     {
@@ -61,44 +65,42 @@ public function __construct($table = null)
     /**
      * Create INTO clause
      *
-     * @param  string|TableIdentifier $table
-     * @return self Provides a fluent interface
+     * @param string|TableIdentifier $table
+     * @return $this
      */
-    public function into($table)
+    public function into($table) : self
     {
         $this->table = $table;
+
         return $this;
     }
 
-    /**
-     * Specify columns
-     *
-     * @param  array $columns
-     * @return self Provides a fluent interface
-     */
-    public function columns(array $columns)
+    public function columns(array $columns) : self
     {
         $this->columns = array_flip($columns);
+
         return $this;
     }
 
     /**
      * Specify values to insert
      *
-     * @param  array|Select $values
-     * @param  string $flag one of VALUES_MERGE or VALUES_SET; defaults to VALUES_SET
-     * @return self Provides a fluent interface
+     * @param array|Select $values
+     * @param string       $flag one of VALUES_MERGE or VALUES_SET; defaults to VALUES_SET
+     * @return $this
      * @throws Exception\InvalidArgumentException
      */
-    public function values($values, $flag = self::VALUES_SET)
+    public function values($values, string $flag = self::VALUES_SET) : self
     {
         if ($values instanceof Select) {
-            if ($flag == self::VALUES_MERGE) {
+            if ($flag === self::VALUES_MERGE) {
                 throw new Exception\InvalidArgumentException(
                     'A Zend\Db\Sql\Select instance cannot be provided with the merge flag'
                 );
             }
+
             $this->select = $values;
+
             return $this;
         }
 
@@ -108,15 +110,15 @@ public function values($values, $flag = self::VALUES_SET)
             );
         }
 
-        if ($this->select && $flag == self::VALUES_MERGE) {
+        if ($this->select && $flag === self::VALUES_MERGE) {
             throw new Exception\InvalidArgumentException(
                 'An array of values cannot be provided with the merge flag when a Zend\Db\Sql\Select instance already '
                 . 'exists as the value source'
             );
         }
 
-        if ($flag == self::VALUES_SET) {
-            $this->columns = $this->isAssocativeArray($values)
+        if ($flag === self::VALUES_SET) {
+            $this->columns = $this->isAssociativeArray($values)
                 ? $values
                 : array_combine(array_keys($this->columns), array_values($values));
         } else {
@@ -124,6 +126,7 @@ public function values($values, $flag = self::VALUES_SET)
                 $this->columns[$column] = $value;
             }
         }
+
         return $this;
     }
 
@@ -135,42 +138,31 @@ public function values($values, $flag = self::VALUES_SET)
      * @param array $array
      * @return bool
      */
-    private function isAssocativeArray(array $array)
+    private function isAssociativeArray(array $array) : bool
     {
         return array_keys($array) !== range(0, count($array) - 1);
     }
 
-    /**
-     * Create INTO SELECT clause
-     *
-     * @param Select $select
-     * @return self
-     */
-    public function select(Select $select)
+    public function select(Select $select) : self
     {
         return $this->values($select);
     }
 
-    /**
-     * Get raw state
-     *
-     * @param string $key
-     * @return mixed
-     */
-    public function getRawState($key = null)
+    public function getRawState(?string $key = null)
     {
         $rawState = [
-            'table' => $this->table,
+            'table'   => $this->table,
             'columns' => array_keys($this->columns),
-            'values' => array_values($this->columns)
+            'values'  => array_values($this->columns),
         ];
+
         return (isset($key) && array_key_exists($key, $rawState)) ? $rawState[$key] : $rawState;
     }
 
     protected function processInsert(
-        PlatformInterface $platform,
-        DriverInterface $driver = null,
-        ParameterContainer $parameterContainer = null
+        PlatformInterface   $platform,
+        ?DriverInterface    $driver = null,
+        ?ParameterContainer $parameterContainer = null
     ) {
         if ($this->select) {
             return;
@@ -191,6 +183,7 @@ protected function processInsert(
                 if ($driver instanceof Pdo) {
                     $column = 'c_' . $i++;
                 }
+
                 $values[] = $driver->formatParameterName($column);
                 $parameterContainer->offsetSet($column, $value);
             } else {
@@ -202,6 +195,7 @@ protected function processInsert(
                 );
             }
         }
+
         return sprintf(
             $this->specifications[static::SPECIFICATION_INSERT],
             $this->resolveTable($this->table, $platform, $driver, $parameterContainer),
@@ -212,8 +206,8 @@ protected function processInsert(
 
     protected function processSelect(
         PlatformInterface $platform,
-        DriverInterface $driver = null,
-        ParameterContainer $parameterContainer = null
+        ?DriverInterface $driver = null,
+        ?ParameterContainer $parameterContainer = null
     ) {
         if (! $this->select) {
             return;
@@ -226,36 +220,18 @@ protected function processSelect(
         return sprintf(
             $this->specifications[static::SPECIFICATION_SELECT],
             $this->resolveTable($this->table, $platform, $driver, $parameterContainer),
-            $columns ? "($columns)" : "",
+            $columns ? "($columns)" : '',
             $selectSql
         );
     }
 
-    /**
-     * Overloading: variable setting
-     *
-     * Proxies to values, using VALUES_MERGE strategy
-     *
-     * @param  string $name
-     * @param  mixed $value
-     * @return self Provides a fluent interface
-     */
-    public function __set($name, $value)
+    public function __set(string $name, $value)
     {
         $this->columns[$name] = $value;
         return $this;
     }
 
-    /**
-     * Overloading: variable unset
-     *
-     * Proxies to values and columns
-     *
-     * @param  string $name
-     * @throws Exception\InvalidArgumentException
-     * @return void
-     */
-    public function __unset($name)
+    public function __unset(string $name)
     {
         if (! array_key_exists($name, $this->columns)) {
             throw new Exception\InvalidArgumentException(
@@ -266,35 +242,19 @@ public function __unset($name)
         unset($this->columns[$name]);
     }
 
-    /**
-     * Overloading: variable isset
-     *
-     * Proxies to columns; does a column of that name exist?
-     *
-     * @param  string $name
-     * @return bool
-     */
-    public function __isset($name)
+    public function __isset(string $name)
     {
         return array_key_exists($name, $this->columns);
     }
 
-    /**
-     * Overloading: variable retrieval
-     *
-     * Retrieves value by column name
-     *
-     * @param  string $name
-     * @throws Exception\InvalidArgumentException
-     * @return mixed
-     */
-    public function __get($name)
+    public function __get(string $name)
     {
         if (! array_key_exists($name, $this->columns)) {
             throw new Exception\InvalidArgumentException(
                 'The key ' . $name . ' was not found in this objects column list'
             );
         }
+
         return $this->columns[$name];
     }
 }
diff --git a/src/Sql/Join.php b/src/Sql/Join.php
index 12e8599663..8f6ad332bb 100644
--- a/src/Sql/Join.php
+++ b/src/Sql/Join.php
@@ -1,14 +1,22 @@
 <?php
 /**
- * @link      http://github.com/zendframework/zend-db for the canonical source repository
- * @copyright Copyright (c) 2005-2016 Zend Technologies USA Inc. (http://www.zend.com)
- * @license   http://framework.zend.com/license/new-bsd New BSD License
+ * @see       https://github.com/zendframework/zend-db for the canonical source repository
+ * @copyright Copyright (c) 2005-2019 Zend Technologies USA Inc. (https://www.zend.com)
+ * @license   https://github.com/zendframework/zend-db/blob/master/LICENSE.md New BSD License
  */
 
+declare(strict_types=1);
+
 namespace Zend\Db\Sql;
 
 use Countable;
 use Iterator;
+use function array_shift;
+use function count;
+use function is_array;
+use function is_string;
+use function key;
+use function sprintf;
 
 /**
  * Aggregate JOIN specifications.
@@ -24,85 +32,45 @@
  */
 class Join implements Iterator, Countable
 {
-    const JOIN_INNER       = 'inner';
-    const JOIN_OUTER       = 'outer';
-    const JOIN_LEFT        = 'left';
-    const JOIN_RIGHT       = 'right';
-    const JOIN_RIGHT_OUTER = 'right outer';
-    const JOIN_LEFT_OUTER  = 'left outer';
-
-    /**
-     * Current iterator position.
-     *
-     * @var int
-     */
+    public const JOIN_INNER       = 'inner';
+    public const JOIN_OUTER       = 'outer';
+    public const JOIN_LEFT        = 'left';
+    public const JOIN_RIGHT       = 'right';
+    public const JOIN_RIGHT_OUTER = 'right outer';
+    public const JOIN_LEFT_OUTER  = 'left outer';
+
+    /** @var int */
     private $position = 0;
 
-    /**
-     * JOIN specifications
-     *
-     * @var array
-     */
+    /** @var array */
     protected $joins = [];
 
-    /**
-     * Initialize iterator position.
-     */
-    public function __construct()
+    public function rewind() : void
     {
         $this->position = 0;
     }
 
-    /**
-     * Rewind iterator.
-     */
-    public function rewind()
-    {
-        $this->position = 0;
-    }
-
-    /**
-     * Return current join specification.
-     *
-     * @return array
-     */
-    public function current()
+    public function current() : array
     {
         return $this->joins[$this->position];
     }
 
-    /**
-     * Return the current iterator index.
-     *
-     * @return int
-     */
-    public function key()
+    public function key() : int
     {
         return $this->position;
     }
 
-    /**
-     * Advance to the next JOIN specification.
-     */
-    public function next()
+    public function next() : void
     {
         ++$this->position;
     }
 
-    /**
-     * Is the iterator at a valid position?
-     *
-     * @return bool
-     */
-    public function valid()
+    public function valid() : bool
     {
         return isset($this->joins[$this->position]);
     }
 
-    /**
-     * @return array
-     */
-    public function getJoins()
+    public function getJoins() : array
     {
         return $this->joins;
     }
@@ -115,10 +83,10 @@ public function getJoins()
      *     of column names, or (a) specification(s) such as SQL_STAR representing
      *     the columns to join.
      * @param string $type The JOIN type to use; see the JOIN_* constants.
-     * @return self Provides a fluent interface
+     * @return $this
      * @throws Exception\InvalidArgumentException for invalid $name values.
      */
-    public function join($name, $on, $columns = [Select::SQL_STAR], $type = Join::JOIN_INNER)
+    public function join($name, $on, $columns = [Select::SQL_STAR], string $type = Join::JOIN_INNER) : self
     {
         if (is_array($name) && (! is_string(key($name)) || count($name) !== 1)) {
             throw new Exception\InvalidArgumentException(
@@ -134,29 +102,20 @@ public function join($name, $on, $columns = [Select::SQL_STAR], $type = Join::JO
             'name'    => $name,
             'on'      => $on,
             'columns' => $columns,
-            'type'    => $type ? $type : Join::JOIN_INNER
+            'type'    => $type ? $type : self::JOIN_INNER,
         ];
 
         return $this;
     }
 
-    /**
-     * Reset to an empty list of JOIN specifications.
-     *
-     * @return self Provides a fluent interface
-     */
-    public function reset()
+    public function reset() : self
     {
         $this->joins = [];
+
         return $this;
     }
 
-    /**
-     * Get count of attached predicates
-     *
-     * @return int
-     */
-    public function count()
+    public function count() : int
     {
         return count($this->joins);
     }
diff --git a/src/Sql/Literal.php b/src/Sql/Literal.php
index a04b0f16de..042c67ac8c 100644
--- a/src/Sql/Literal.php
+++ b/src/Sql/Literal.php
@@ -1,56 +1,43 @@
 <?php
 /**
- * Zend Framework (http://framework.zend.com/)
- *
- * @link      http://github.com/zendframework/zf2 for the canonical source repository
- * @copyright Copyright (c) 2005-2016 Zend Technologies USA Inc. (http://www.zend.com)
- * @license   http://framework.zend.com/license/new-bsd New BSD License
+ * @see       https://github.com/zendframework/zend-db for the canonical source repository
+ * @copyright Copyright (c) 2005-2019 Zend Technologies USA Inc. (https://www.zend.com)
+ * @license   https://github.com/zendframework/zend-db/blob/master/LICENSE.md New BSD License
  */
 
+declare(strict_types=1);
+
 namespace Zend\Db\Sql;
 
+use function str_replace;
+
 class Literal implements ExpressionInterface
 {
-    /**
-     * @var string
-     */
-    protected $literal = '';
-
-    /**
-     * @param $literal
-     */
-    public function __construct($literal = '')
+    protected $literal;
+
+    public function __construct(string $literal = '')
     {
         $this->literal = $literal;
     }
 
-    /**
-     * @param string $literal
-     * @return self Provides a fluent interface
-     */
-    public function setLiteral($literal)
+    public function setLiteral(string $literal) : self
     {
         $this->literal = $literal;
+
         return $this;
     }
 
-    /**
-     * @return string
-     */
-    public function getLiteral()
+    public function getLiteral() : string
     {
         return $this->literal;
     }
 
-    /**
-     * @return array
-     */
-    public function getExpressionData()
+    public function getExpressionData() : array
     {
         return [[
             str_replace('%', '%%', $this->literal),
             [],
-            []
+            [],
         ]];
     }
 }
diff --git a/src/Sql/Platform/AbstractPlatform.php b/src/Sql/Platform/AbstractPlatform.php
index 6d0b040bc6..7efc815f40 100644
--- a/src/Sql/Platform/AbstractPlatform.php
+++ b/src/Sql/Platform/AbstractPlatform.php
@@ -1,36 +1,29 @@
 <?php
 /**
- * Zend Framework (http://framework.zend.com/)
- *
- * @link      http://github.com/zendframework/zf2 for the canonical source repository
- * @copyright Copyright (c) 2005-2016 Zend Technologies USA Inc. (http://www.zend.com)
- * @license   http://framework.zend.com/license/new-bsd New BSD License
+ * @see       https://github.com/zendframework/zend-db for the canonical source repository
+ * @copyright Copyright (c) 2005-2019 Zend Technologies USA Inc. (https://www.zend.com)
+ * @license   https://github.com/zendframework/zend-db/blob/master/LICENSE.md New BSD License
  */
 
+declare(strict_types=1);
+
 namespace Zend\Db\Sql\Platform;
 
 use Zend\Db\Adapter\AdapterInterface;
 use Zend\Db\Adapter\Platform\PlatformInterface;
 use Zend\Db\Adapter\StatementContainerInterface;
-use Zend\Db\Sql\Exception;
+use Zend\Db\Sql\Exception\RuntimeException;
 use Zend\Db\Sql\PreparableSqlInterface;
 use Zend\Db\Sql\SqlInterface;
 
 class AbstractPlatform implements PlatformDecoratorInterface, PreparableSqlInterface, SqlInterface
 {
-    /**
-     * @var object|null
-     */
+    /** @var object|null */
     protected $subject;
 
-    /**
-     * @var PlatformDecoratorInterface[]
-     */
+    /** @var PlatformDecoratorInterface[] */
     protected $decorators = [];
 
-    /**
-     * {@inheritDoc}
-     */
     public function setSubject($subject)
     {
         $this->subject = $subject;
@@ -38,13 +31,7 @@ public function setSubject($subject)
         return $this;
     }
 
-    /**
-     * @param string                     $type
-     * @param PlatformDecoratorInterface $decorator
-     *
-     * @return void
-     */
-    public function setTypeDecorator($type, PlatformDecoratorInterface $decorator)
+    public function setTypeDecorator(string $type, PlatformDecoratorInterface $decorator) : void
     {
         $this->decorators[$type] = $decorator;
     }
@@ -67,22 +54,17 @@ public function getTypeDecorator($subject)
     }
 
     /**
-     * @return array|PlatformDecoratorInterface[]
+     * @return array|PlatformDecoratorInterface
      */
     public function getDecorators()
     {
         return $this->decorators;
     }
 
-    /**
-     * {@inheritDoc}
-     *
-     * @throws Exception\RuntimeException
-     */
     public function prepareStatement(AdapterInterface $adapter, StatementContainerInterface $statementContainer)
     {
         if (! $this->subject instanceof PreparableSqlInterface) {
-            throw new Exception\RuntimeException(
+            throw new RuntimeException(
                 'The subject does not appear to implement Zend\Db\Sql\PreparableSqlInterface, thus calling '
                 . 'prepareStatement() has no effect'
             );
@@ -93,15 +75,10 @@ public function prepareStatement(AdapterInterface $adapter, StatementContainerIn
         return $statementContainer;
     }
 
-    /**
-     * {@inheritDoc}
-     *
-     * @throws Exception\RuntimeException
-     */
-    public function getSqlString(PlatformInterface $adapterPlatform = null)
+    public function getSqlString(?PlatformInterface $adapterPlatform = null) : string
     {
         if (! $this->subject instanceof SqlInterface) {
-            throw new Exception\RuntimeException(
+            throw new RuntimeException(
                 'The subject does not appear to implement Zend\Db\Sql\SqlInterface, thus calling '
                 . 'prepareStatement() has no effect'
             );
diff --git a/src/Sql/Platform/IbmDb2/IbmDb2.php b/src/Sql/Platform/IbmDb2/IbmDb2.php
index 35ddc2c768..5e4b31c914 100644
--- a/src/Sql/Platform/IbmDb2/IbmDb2.php
+++ b/src/Sql/Platform/IbmDb2/IbmDb2.php
@@ -1,23 +1,21 @@
 <?php
 /**
- * Zend Framework (http://framework.zend.com/)
- *
- * @link      http://github.com/zendframework/zf2 for the canonical source repository
- * @copyright Copyright (c) 2005-2016 Zend Technologies USA Inc. (http://www.zend.com)
- * @license   http://framework.zend.com/license/new-bsd New BSD License
+ * @see       https://github.com/zendframework/zend-db for the canonical source repository
+ * @copyright Copyright (c) 2005-2019 Zend Technologies USA Inc. (https://www.zend.com)
+ * @license   https://github.com/zendframework/zend-db/blob/master/LICENSE.md New BSD License
  */
 
+declare(strict_types=1);
+
 namespace Zend\Db\Sql\Platform\IbmDb2;
 
 use Zend\Db\Sql\Platform\AbstractPlatform;
+use Zend\Db\Sql\Select;
 
 class IbmDb2 extends AbstractPlatform
 {
-    /**
-     * @param SelectDecorator $selectDecorator
-     */
-    public function __construct(SelectDecorator $selectDecorator = null)
+    public function __construct(?SelectDecorator $selectDecorator = null)
     {
-        $this->setTypeDecorator('Zend\Db\Sql\Select', ($selectDecorator) ?: new SelectDecorator());
+        $this->setTypeDecorator(Select::class, $selectDecorator ?? new SelectDecorator());
     }
 }
diff --git a/src/Sql/Platform/IbmDb2/SelectDecorator.php b/src/Sql/Platform/IbmDb2/SelectDecorator.php
index f1988c09b5..7a57be6f52 100644
--- a/src/Sql/Platform/IbmDb2/SelectDecorator.php
+++ b/src/Sql/Platform/IbmDb2/SelectDecorator.php
@@ -1,12 +1,12 @@
 <?php
 /**
- * Zend Framework (http://framework.zend.com/)
- *
- * @link      http://github.com/zendframework/zf2 for the canonical source repository
- * @copyright Copyright (c) 2005-2016 Zend Technologies USA Inc. (http://www.zend.com)
- * @license   http://framework.zend.com/license/new-bsd New BSD License
+ * @see       https://github.com/zendframework/zend-db for the canonical source repository
+ * @copyright Copyright (c) 2005-2019 Zend Technologies USA Inc. (https://www.zend.com)
+ * @license   https://github.com/zendframework/zend-db/blob/master/LICENSE.md New BSD License
  */
 
+declare(strict_types=1);
+
 namespace Zend\Db\Sql\Platform\IbmDb2;
 
 use Zend\Db\Adapter\Driver\DriverInterface;
@@ -14,37 +14,30 @@
 use Zend\Db\Adapter\Platform\PlatformInterface;
 use Zend\Db\Sql\Platform\PlatformDecoratorInterface;
 use Zend\Db\Sql\Select;
+use function array_shift;
+use function array_unshift;
+use function current;
+use function preg_match;
+use function sprintf;
+use function strpos;
 
 class SelectDecorator extends Select implements PlatformDecoratorInterface
 {
-    /**
-     * @var bool
-     */
+    /** @var bool */
     protected $isSelectContainDistinct = false;
 
-    /**
-     * @var Select
-     */
-    protected $subject = null;
+    /** @var Select */
+    protected $subject;
 
-     /**
-     * @var bool
-     */
+     /** @var bool */
     protected $supportsLimitOffset = false;
 
-
-   /**
-     * @return bool
-     */
-    public function getIsSelectContainDistinct()
+    public function getIsSelectContainDistinct() : bool
     {
         return $this->isSelectContainDistinct;
     }
 
-    /**
-     * @param boolean $isSelectContainDistinct
-     */
-    public function setIsSelectContainDistinct($isSelectContainDistinct)
+    public function setIsSelectContainDistinct(bool $isSelectContainDistinct) : void
     {
         $this->isSelectContainDistinct = $isSelectContainDistinct;
     }
@@ -57,33 +50,25 @@ public function setSubject($select)
         $this->subject = $select;
     }
 
-    /**
-     * @return bool
-     */
-    public function getSupportsLimitOffset()
+    public function getSupportsLimitOffset() : bool
     {
         return $this->supportsLimitOffset;
     }
 
-    /**
-     * @param bool $supportsLimitOffset
-     */
-    public function setSupportsLimitOffset($supportsLimitOffset)
+    public function setSupportsLimitOffset(bool $supportsLimitOffset) : void
     {
         $this->supportsLimitOffset = $supportsLimitOffset;
     }
 
-    /**
-     * @see Select::renderTable
-     */
-    protected function renderTable($table, $alias = null)
+    protected function renderTable(string $table, ?string $alias = null) : string
     {
         return $table . ' ' . $alias;
     }
 
-    protected function localizeVariables()
+    protected function localizeVariables() : void
     {
         parent::localizeVariables();
+
         // set specifications
         unset($this->specifications[self::LIMIT]);
         unset($this->specifications[self::OFFSET]);
@@ -91,20 +76,13 @@ protected function localizeVariables()
         $this->specifications['LIMITOFFSET'] = null;
     }
 
-    /**
-     * @param  PlatformInterface  $platform
-     * @param  DriverInterface    $driver
-     * @param  ParameterContainer $parameterContainer
-     * @param  array              $sqls
-     * @param  array              $parameters
-     */
     protected function processLimitOffset(
-        PlatformInterface $platform,
-        DriverInterface $driver = null,
-        ParameterContainer $parameterContainer = null,
-        &$sqls,
-        &$parameters
-    ) {
+        PlatformInterface   $platform,
+        ?DriverInterface    $driver = null,
+        ?ParameterContainer $parameterContainer = null,
+        array              &$sqls,
+        array              &$parameters
+    ) : void {
         if ($this->limit === null && $this->offset === null) {
             return;
         }
@@ -112,26 +90,30 @@ protected function processLimitOffset(
         if ($this->supportsLimitOffset) {
             // Note: db2_prepare/db2_execute fails with positional parameters, for LIMIT & OFFSET
             $limit = (int) $this->limit;
+
             if (! $limit) {
                 return;
             }
 
             $offset = (int) $this->offset;
+
             if ($offset) {
-                array_push($sqls, sprintf("LIMIT %s OFFSET %s", $limit, $offset));
+                $sqls[] = sprintf('LIMIT %s OFFSET %s', $limit, $offset);
                 return;
             }
 
-            array_push($sqls, sprintf("LIMIT %s", $limit));
+            $sqls[] = sprintf('LIMIT %s', $limit);
+
             return;
         }
 
         $selectParameters = $parameters[self::SELECT];
 
         $starSuffix = $platform->getIdentifierSeparator() . self::SQL_STAR;
+
         foreach ($selectParameters[0] as $i => $columnParameters) {
-            if ($columnParameters[0] == self::SQL_STAR
-                || (isset($columnParameters[1]) && $columnParameters[1] == self::SQL_STAR)
+            if ($columnParameters[0] === self::SQL_STAR
+                || (isset($columnParameters[1]) && $columnParameters[1] === self::SQL_STAR)
                 || strpos($columnParameters[0], $starSuffix)
             ) {
                 $selectParameters[0] = [[self::SQL_STAR]];
@@ -156,16 +138,16 @@ protected function processLimitOffset(
 
         if ($parameterContainer) {
             // create bottom part of query, with offset and limit using row_number
-            $limitParamName        = $driver->formatParameterName('limit');
-            $offsetParamName       = $driver->formatParameterName('offset');
+            $limitParamName  = $driver->formatParameterName('limit');
+            $offsetParamName = $driver->formatParameterName('offset');
 
-            array_push($sqls, sprintf(
-                // @codingStandardsIgnoreStart
-                ") AS ZEND_IBMDB2_SERVER_LIMIT_OFFSET_EMULATION WHERE ZEND_IBMDB2_SERVER_LIMIT_OFFSET_EMULATION.ZEND_DB_ROWNUM BETWEEN %s AND %s",
+            $sqls[] = sprintf(
+            // @codingStandardsIgnoreStart
+                ') AS ZEND_IBMDB2_SERVER_LIMIT_OFFSET_EMULATION WHERE ZEND_IBMDB2_SERVER_LIMIT_OFFSET_EMULATION.ZEND_DB_ROWNUM BETWEEN %s AND %s',
                 // @codingStandardsIgnoreEnd
                 $offsetParamName,
                 $limitParamName
-            ));
+            );
 
             if ((int) $this->offset > 0) {
                 $parameterContainer->offsetSet('offset', (int) $this->offset + 1);
@@ -181,17 +163,18 @@ protected function processLimitOffset(
                 $offset = (int) $this->offset;
             }
 
-            array_push($sqls, sprintf(
-                // @codingStandardsIgnoreStart
-                ") AS ZEND_IBMDB2_SERVER_LIMIT_OFFSET_EMULATION WHERE ZEND_IBMDB2_SERVER_LIMIT_OFFSET_EMULATION.ZEND_DB_ROWNUM BETWEEN %d AND %d",
+            $sqls[] = sprintf(
+            // @codingStandardsIgnoreStart
+                ') AS ZEND_IBMDB2_SERVER_LIMIT_OFFSET_EMULATION WHERE ZEND_IBMDB2_SERVER_LIMIT_OFFSET_EMULATION.ZEND_DB_ROWNUM BETWEEN %d AND %d',
                 // @codingStandardsIgnoreEnd
                 $offset,
                 (int) $this->limit + (int) $this->offset
-            ));
+            );
         }
 
         if (isset($sqls[self::ORDER])) {
             $orderBy = $sqls[self::ORDER];
+
             unset($sqls[self::ORDER]);
         } else {
             $orderBy = '';
diff --git a/src/Sql/Platform/Mysql/Ddl/AlterTableDecorator.php b/src/Sql/Platform/Mysql/Ddl/AlterTableDecorator.php
index ea3176532d..b392a679b6 100644
--- a/src/Sql/Platform/Mysql/Ddl/AlterTableDecorator.php
+++ b/src/Sql/Platform/Mysql/Ddl/AlterTableDecorator.php
@@ -1,28 +1,33 @@
 <?php
 /**
- * Zend Framework (http://framework.zend.com/)
- *
- * @link      http://github.com/zendframework/zf2 for the canonical source repository
- * @copyright Copyright (c) 2005-2016 Zend Technologies USA Inc. (http://www.zend.com)
- * @license   http://framework.zend.com/license/new-bsd New BSD License
+ * @see       https://github.com/zendframework/zend-db for the canonical source repository
+ * @copyright Copyright (c) 2005-2019 Zend Technologies USA Inc. (https://www.zend.com)
+ * @license   https://github.com/zendframework/zend-db/blob/master/LICENSE.md New BSD License
  */
 
+declare(strict_types=1);
+
 namespace Zend\Db\Sql\Platform\Mysql\Ddl;
 
 use Zend\Db\Adapter\Platform\PlatformInterface;
 use Zend\Db\Sql\Ddl\AlterTable;
 use Zend\Db\Sql\Platform\PlatformDecoratorInterface;
+use function count;
+use function range;
+use function str_replace;
+use function strlen;
+use function strpos;
+use function strtolower;
+use function strtoupper;
+use function substr_replace;
+use function uksort;
 
 class AlterTableDecorator extends AlterTable implements PlatformDecoratorInterface
 {
-    /**
-     * @var AlterTable
-     */
+    /** @var AlterTable */
     protected $subject;
 
-    /**
-     * @var int[]
-     */
+    /** @var int[] */
     protected $columnOptionSortOrder = [
         'unsigned'      => 0,
         'zerofill'      => 1,
@@ -38,9 +43,9 @@ class AlterTableDecorator extends AlterTable implements PlatformDecoratorInterfa
 
     /**
      * @param AlterTable $subject
-     * @return self Provides a fluent interface
+     * @return $this
      */
-    public function setSubject($subject)
+    public function setSubject($subject) : self
     {
         $this->subject = $subject;
 
@@ -51,7 +56,7 @@ public function setSubject($subject)
      * @param string $sql
      * @return array
      */
-    protected function getSqlInsertOffsets($sql)
+    protected function getSqlInsertOffsets(string $sql) : array
     {
         $sqlLength   = strlen($sql);
         $insertStart = [];
@@ -81,11 +86,7 @@ protected function getSqlInsertOffsets($sql)
         return $insertStart;
     }
 
-    /**
-     * @param PlatformInterface $adapterPlatform
-     * @return array
-     */
-    protected function processAddColumns(PlatformInterface $adapterPlatform = null)
+    protected function processAddColumns(?PlatformInterface $adapterPlatform = null) : array
     {
         $sqls = [];
 
@@ -106,11 +107,11 @@ protected function processAddColumns(PlatformInterface $adapterPlatform = null)
                 switch ($this->normalizeColumnOption($coName)) {
                     case 'unsigned':
                         $insert = ' UNSIGNED';
-                        $j = 0;
+                        $j      = 0;
                         break;
                     case 'zerofill':
                         $insert = ' ZEROFILL';
-                        $j = 0;
+                        $j      = 0;
                         break;
                     case 'identity':
                     case 'serial':
@@ -120,43 +121,43 @@ protected function processAddColumns(PlatformInterface $adapterPlatform = null)
                         break;
                     case 'comment':
                         $insert = ' COMMENT ' . $adapterPlatform->quoteValue($coValue);
-                        $j = 2;
+                        $j      = 2;
                         break;
                     case 'columnformat':
                     case 'format':
                         $insert = ' COLUMN_FORMAT ' . strtoupper($coValue);
-                        $j = 2;
+                        $j      = 2;
                         break;
                     case 'storage':
                         $insert = ' STORAGE ' . strtoupper($coValue);
-                        $j = 2;
+                        $j      = 2;
                         break;
                     case 'after':
                         $insert = ' AFTER ' . $adapterPlatform->quoteIdentifier($coValue);
-                        $j = 2;
+                        $j      = 2;
                 }
 
                 if ($insert) {
-                    $j = isset($j) ? $j : 0;
-                    $sql = substr_replace($sql, $insert, $insertStart[$j], 0);
+                    $j                = isset($j) ? $j : 0;
+                    $sql              = substr_replace($sql, $insert, $insertStart[$j], 0);
                     $insertStartCount = count($insertStart);
+
                     for (; $j < $insertStartCount; ++$j) {
                         $insertStart[$j] += strlen($insert);
                     }
                 }
             }
+
             $sqls[$i] = $sql;
         }
+
         return [$sqls];
     }
 
-    /**
-     * @param PlatformInterface $adapterPlatform
-     * @return array
-     */
-    protected function processChangeColumns(PlatformInterface $adapterPlatform = null)
+    protected function processChangeColumns(?PlatformInterface $adapterPlatform = null) : array
     {
         $sqls = [];
+
         foreach ($this->changeColumns as $name => $column) {
             $sql           = $this->processExpression($column, $adapterPlatform);
             $insertStart   = $this->getSqlInsertOffsets($sql);
@@ -210,6 +211,7 @@ protected function processChangeColumns(PlatformInterface $adapterPlatform = nul
                     }
                 }
             }
+
             $sqls[] = [
                 $adapterPlatform->quoteIdentifier($name),
                 $sql
@@ -219,24 +221,12 @@ protected function processChangeColumns(PlatformInterface $adapterPlatform = nul
         return [$sqls];
     }
 
-    /**
-     * @param string $name
-     *
-     * @return string
-     */
-    private function normalizeColumnOption($name)
+    private function normalizeColumnOption(string $name) : string
     {
         return strtolower(str_replace(['-', '_', ' '], '', $name));
     }
 
-    /**
-     *
-     * @param string $columnA
-     * @param string $columnB
-     *
-     * @return int
-     */
-    private function compareColumnOptions($columnA, $columnB)
+    private function compareColumnOptions(string $columnA, string $columnB) : int
     {
         $columnA = $this->normalizeColumnOption($columnA);
         $columnA = isset($this->columnOptionSortOrder[$columnA])
diff --git a/src/Sql/Platform/Mysql/Ddl/CreateTableDecorator.php b/src/Sql/Platform/Mysql/Ddl/CreateTableDecorator.php
index fa8815a9a1..2acea2b82c 100644
--- a/src/Sql/Platform/Mysql/Ddl/CreateTableDecorator.php
+++ b/src/Sql/Platform/Mysql/Ddl/CreateTableDecorator.php
@@ -1,28 +1,32 @@
 <?php
 /**
- * Zend Framework (http://framework.zend.com/)
- *
- * @link      http://github.com/zendframework/zf2 for the canonical source repository
- * @copyright Copyright (c) 2005-2016 Zend Technologies USA Inc. (http://www.zend.com)
- * @license   http://framework.zend.com/license/new-bsd New BSD License
+ * @see       https://github.com/zendframework/zend-db for the canonical source repository
+ * @copyright Copyright (c) 2005-2019 Zend Technologies USA Inc. (https://www.zend.com)
+ * @license   https://github.com/zendframework/zend-db/blob/master/LICENSE.md New BSD License
  */
 
+declare(strict_types=1);
+
 namespace Zend\Db\Sql\Platform\Mysql\Ddl;
 
 use Zend\Db\Adapter\Platform\PlatformInterface;
 use Zend\Db\Sql\Ddl\CreateTable;
 use Zend\Db\Sql\Platform\PlatformDecoratorInterface;
+use function count;
+use function range;
+use function str_replace;
+use function strlen;
+use function strpos;
+use function strtoupper;
+use function substr_replace;
+use function uksort;
 
 class CreateTableDecorator extends CreateTable implements PlatformDecoratorInterface
 {
-    /**
-     * @var CreateTable
-     */
+    /** @var CreateTable */
     protected $subject;
 
-    /**
-     * @var int[]
-     */
+    /** @var int[] */
     protected $columnOptionSortOrder = [
         'unsigned'      => 0,
         'zerofill'      => 1,
@@ -37,21 +41,16 @@ class CreateTableDecorator extends CreateTable implements PlatformDecoratorInter
 
     /**
      * @param CreateTable $subject
-     *
-     * @return self Provides a fluent interface
+     * @return $this
      */
-    public function setSubject($subject)
+    public function setSubject($subject) : self
     {
         $this->subject = $subject;
 
         return $this;
     }
 
-    /**
-     * @param string $sql
-     * @return array
-     */
-    protected function getSqlInsertOffsets($sql)
+    protected function getSqlInsertOffsets(string $sql) : array
     {
         $sqlLength   = strlen($sql);
         $insertStart = [];
@@ -81,10 +80,7 @@ protected function getSqlInsertOffsets($sql)
         return $insertStart;
     }
 
-    /**
-     * {@inheritDoc}
-     */
-    protected function processColumns(PlatformInterface $platform = null)
+    protected function processColumns(?PlatformInterface $platform = null)
     {
         if (! $this->columns) {
             return;
@@ -109,37 +105,38 @@ protected function processColumns(PlatformInterface $platform = null)
                 switch ($this->normalizeColumnOption($coName)) {
                     case 'unsigned':
                         $insert = ' UNSIGNED';
-                        $j = 0;
+                        $j      = 0;
                         break;
                     case 'zerofill':
                         $insert = ' ZEROFILL';
-                        $j = 0;
+                        $j      = 0;
                         break;
                     case 'identity':
                     case 'serial':
                     case 'autoincrement':
                         $insert = ' AUTO_INCREMENT';
-                        $j = 1;
+                        $j      = 1;
                         break;
                     case 'comment':
                         $insert = ' COMMENT ' . $platform->quoteValue($coValue);
-                        $j = 2;
+                        $j      = 2;
                         break;
                     case 'columnformat':
                     case 'format':
                         $insert = ' COLUMN_FORMAT ' . strtoupper($coValue);
-                        $j = 2;
+                        $j      = 2;
                         break;
                     case 'storage':
                         $insert = ' STORAGE ' . strtoupper($coValue);
-                        $j = 2;
+                        $j      = 2;
                         break;
                 }
 
                 if ($insert) {
-                    $j = isset($j) ? $j : 0;
-                    $sql = substr_replace($sql, $insert, $insertStart[$j], 0);
+                    $j                = isset($j) ? $j : 0;
+                    $sql              = substr_replace($sql, $insert, $insertStart[$j], 0);
                     $insertStartCount = count($insertStart);
+
                     for (; $j < $insertStartCount; ++$j) {
                         $insertStart[$j] += strlen($insert);
                     }
@@ -152,32 +149,22 @@ protected function processColumns(PlatformInterface $platform = null)
         return [$sqls];
     }
 
-    /**
-     * @param string $name
-     *
-     * @return string
-     */
-    private function normalizeColumnOption($name)
+    private function normalizeColumnOption(string $name) : string
     {
         return strtolower(str_replace(['-', '_', ' '], '', $name));
     }
 
-    /**
-     *
-     * @param string $columnA
-     * @param string $columnB
-     *
-     * @return int
-     */
-    private function compareColumnOptions($columnA, $columnB)
+    private function compareColumnOptions(string $columnA, string $columnB) : int
     {
         $columnA = $this->normalizeColumnOption($columnA);
         $columnA = isset($this->columnOptionSortOrder[$columnA])
-            ? $this->columnOptionSortOrder[$columnA] : count($this->columnOptionSortOrder);
+            ? $this->columnOptionSortOrder[$columnA]
+            : count($this->columnOptionSortOrder);
 
         $columnB = $this->normalizeColumnOption($columnB);
         $columnB = isset($this->columnOptionSortOrder[$columnB])
-            ? $this->columnOptionSortOrder[$columnB] : count($this->columnOptionSortOrder);
+            ? $this->columnOptionSortOrder[$columnB]
+            : count($this->columnOptionSortOrder);
 
         return $columnA - $columnB;
     }
diff --git a/src/Sql/Platform/Mysql/Mysql.php b/src/Sql/Platform/Mysql/Mysql.php
index 3e1611b87f..321aa2229f 100644
--- a/src/Sql/Platform/Mysql/Mysql.php
+++ b/src/Sql/Platform/Mysql/Mysql.php
@@ -1,22 +1,27 @@
 <?php
 /**
- * Zend Framework (http://framework.zend.com/)
- *
- * @link      http://github.com/zendframework/zf2 for the canonical source repository
- * @copyright Copyright (c) 2005-2016 Zend Technologies USA Inc. (http://www.zend.com)
- * @license   http://framework.zend.com/license/new-bsd New BSD License
+ * @see       https://github.com/zendframework/zend-db for the canonical source repository
+ * @copyright Copyright (c) 2005-2019 Zend Technologies USA Inc. (https://www.zend.com)
+ * @license   https://github.com/zendframework/zend-db/blob/master/LICENSE.md New BSD License
  */
 
+declare(strict_types=1);
+
 namespace Zend\Db\Sql\Platform\Mysql;
 
 use Zend\Db\Sql\Platform\AbstractPlatform;
+use Zend\Db\Sql\Ddl\AlterTable;
+use Zend\Db\Sql\Ddl\CreateTable;
+use Zend\Db\Sql\Platform\Mysql\Ddl\AlterTableDecorator;
+use Zend\Db\Sql\Platform\Mysql\Ddl\CreateTableDecorator;
+use Zend\Db\Sql\Select;
 
 class Mysql extends AbstractPlatform
 {
     public function __construct()
     {
-        $this->setTypeDecorator('Zend\Db\Sql\Select', new SelectDecorator());
-        $this->setTypeDecorator('Zend\Db\Sql\Ddl\CreateTable', new Ddl\CreateTableDecorator());
-        $this->setTypeDecorator('Zend\Db\Sql\Ddl\AlterTable', new Ddl\AlterTableDecorator());
+        $this->setTypeDecorator(Select::class, new SelectDecorator());
+        $this->setTypeDecorator(CreateTable::class, new CreateTableDecorator());
+        $this->setTypeDecorator(AlterTable::class, new AlterTableDecorator());
     }
 }
diff --git a/src/Sql/Platform/Mysql/SelectDecorator.php b/src/Sql/Platform/Mysql/SelectDecorator.php
index 3ef7655ce8..a703efa734 100644
--- a/src/Sql/Platform/Mysql/SelectDecorator.php
+++ b/src/Sql/Platform/Mysql/SelectDecorator.php
@@ -1,12 +1,12 @@
 <?php
 /**
- * Zend Framework (http://framework.zend.com/)
- *
- * @link      http://github.com/zendframework/zf2 for the canonical source repository
- * @copyright Copyright (c) 2005-2016 Zend Technologies USA Inc. (http://www.zend.com)
- * @license   http://framework.zend.com/license/new-bsd New BSD License
+ * @see       https://github.com/zendframework/zend-db for the canonical source repository
+ * @copyright Copyright (c) 2005-2019 Zend Technologies USA Inc. (https://www.zend.com)
+ * @license   https://github.com/zendframework/zend-db/blob/master/LICENSE.md New BSD License
  */
 
+declare(strict_types=1);
+
 namespace Zend\Db\Sql\Platform\Mysql;
 
 use Zend\Db\Adapter\Driver\DriverInterface;
@@ -17,10 +17,8 @@
 
 class SelectDecorator extends Select implements PlatformDecoratorInterface
 {
-    /**
-     * @var Select
-     */
-    protected $subject = null;
+    /** @var Select */
+    protected $subject;
 
     /**
      * @param Select $select
@@ -30,7 +28,7 @@ public function setSubject($select)
         $this->subject = $select;
     }
 
-    protected function localizeVariables()
+    protected function localizeVariables() : void
     {
         parent::localizeVariables();
         if ($this->limit === null && $this->offset !== null) {
@@ -39,19 +37,22 @@ protected function localizeVariables()
     }
 
     protected function processLimit(
-        PlatformInterface $platform,
-        DriverInterface $driver = null,
-        ParameterContainer $parameterContainer = null
+        PlatformInterface   $platform,
+        ?DriverInterface    $driver = null,
+        ?ParameterContainer $parameterContainer = null
     ) {
         if ($this->limit === null && $this->offset !== null) {
             return [''];
         }
+
         if ($this->limit === null) {
             return;
         }
+
         if ($parameterContainer) {
             $paramPrefix = $this->processInfo['paramPrefix'];
             $parameterContainer->offsetSet($paramPrefix . 'limit', $this->limit, ParameterContainer::TYPE_INTEGER);
+
             return [$driver->formatParameterName($paramPrefix . 'limit')];
         }
 
@@ -59,9 +60,9 @@ protected function processLimit(
     }
 
     protected function processOffset(
-        PlatformInterface $platform,
-        DriverInterface $driver = null,
-        ParameterContainer $parameterContainer = null
+        PlatformInterface   $platform,
+        ?DriverInterface    $driver = null,
+        ?ParameterContainer $parameterContainer = null
     ) {
         if ($this->offset === null) {
             return;
@@ -69,6 +70,7 @@ protected function processOffset(
         if ($parameterContainer) {
             $paramPrefix = $this->processInfo['paramPrefix'];
             $parameterContainer->offsetSet($paramPrefix . 'offset', $this->offset, ParameterContainer::TYPE_INTEGER);
+
             return [$driver->formatParameterName($paramPrefix . 'offset')];
         }
 
diff --git a/src/Sql/Platform/Oracle/Oracle.php b/src/Sql/Platform/Oracle/Oracle.php
index bf1dc31df5..6f0163e8b3 100644
--- a/src/Sql/Platform/Oracle/Oracle.php
+++ b/src/Sql/Platform/Oracle/Oracle.php
@@ -1,20 +1,21 @@
 <?php
 /**
- * Zend Framework (http://framework.zend.com/)
- *
- * @link      http://github.com/zendframework/zf2 for the canonical source repository
- * @copyright Copyright (c) 2005-2016 Zend Technologies USA Inc. (http://www.zend.com)
- * @license   http://framework.zend.com/license/new-bsd New BSD License
+ * @see       https://github.com/zendframework/zend-db for the canonical source repository
+ * @copyright Copyright (c) 2005-2019 Zend Technologies USA Inc. (https://www.zend.com)
+ * @license   https://github.com/zendframework/zend-db/blob/master/LICENSE.md New BSD License
  */
 
+declare(strict_types=1);
+
 namespace Zend\Db\Sql\Platform\Oracle;
 
 use Zend\Db\Sql\Platform\AbstractPlatform;
+use Zend\Db\Sql\Select;
 
 class Oracle extends AbstractPlatform
 {
-    public function __construct(SelectDecorator $selectDecorator = null)
+    public function __construct(?SelectDecorator $selectDecorator = null)
     {
-        $this->setTypeDecorator('Zend\Db\Sql\Select', ($selectDecorator) ?: new SelectDecorator());
+        $this->setTypeDecorator(Select::class, $selectDecorator ?? new SelectDecorator());
     }
 }
diff --git a/src/Sql/Platform/Oracle/SelectDecorator.php b/src/Sql/Platform/Oracle/SelectDecorator.php
index 9961b4dcf9..ae774778a8 100644
--- a/src/Sql/Platform/Oracle/SelectDecorator.php
+++ b/src/Sql/Platform/Oracle/SelectDecorator.php
@@ -1,12 +1,12 @@
 <?php
 /**
- * Zend Framework (http://framework.zend.com/)
- *
- * @link      http://github.com/zendframework/zf2 for the canonical source repository
- * @copyright Copyright (c) 2005-2016 Zend Technologies USA Inc. (http://www.zend.com)
- * @license   http://framework.zend.com/license/new-bsd New BSD License
+ * @see       https://github.com/zendframework/zend-db for the canonical source repository
+ * @copyright Copyright (c) 2005-2019 Zend Technologies USA Inc. (https://www.zend.com)
+ * @license   https://github.com/zendframework/zend-db/blob/master/LICENSE.md New BSD License
  */
 
+declare(strict_types=1);
+
 namespace Zend\Db\Sql\Platform\Oracle;
 
 use Zend\Db\Adapter\Driver\DriverInterface;
@@ -14,13 +14,14 @@
 use Zend\Db\Adapter\Platform\PlatformInterface;
 use Zend\Db\Sql\Platform\PlatformDecoratorInterface;
 use Zend\Db\Sql\Select;
+use function array_shift;
+use function array_unshift;
+use function strpos;
 
 class SelectDecorator extends Select implements PlatformDecoratorInterface
 {
-    /**
-     * @var Select
-     */
-    protected $subject = null;
+    /** @var Select */
+    protected $subject;
 
     /**
      * @param Select $select
@@ -30,15 +31,12 @@ public function setSubject($select)
         $this->subject = $select;
     }
 
-    /**
-     * @see \Zend\Db\Sql\Select::renderTable
-     */
-    protected function renderTable($table, $alias = null)
+    protected function renderTable(string $table, ?string $alias = null) : string
     {
         return $table . ($alias ? ' ' . $alias : '');
     }
 
-    protected function localizeVariables()
+    protected function localizeVariables() : void
     {
         parent::localizeVariables();
         unset($this->specifications[self::LIMIT]);
@@ -47,21 +45,13 @@ protected function localizeVariables()
         $this->specifications['LIMITOFFSET'] = null;
     }
 
-    /**
-     * @param PlatformInterface $platform
-     * @param DriverInterface $driver
-     * @param ParameterContainer $parameterContainer
-     * @param array $sqls
-     * @param array $parameters
-     * @return null
-     */
     protected function processLimitOffset(
-        PlatformInterface $platform,
-        DriverInterface $driver = null,
-        ParameterContainer $parameterContainer = null,
-        &$sqls = [],
-        &$parameters = []
-    ) {
+        PlatformInterface   $platform,
+        ?DriverInterface    $driver = null,
+        ?ParameterContainer $parameterContainer = null,
+        array              &$sqls = [],
+        array              &$parameters = []
+    ) : void {
         if ($this->limit === null && $this->offset === null) {
             return;
         }
@@ -70,8 +60,8 @@ protected function processLimitOffset(
         $starSuffix = $platform->getIdentifierSeparator() . self::SQL_STAR;
 
         foreach ($selectParameters[0] as $i => $columnParameters) {
-            if ($columnParameters[0] == self::SQL_STAR
-                || (isset($columnParameters[1]) && $columnParameters[1] == self::SQL_STAR)
+            if ($columnParameters[0] === self::SQL_STAR
+                || (isset($columnParameters[1]) && $columnParameters[1] === self::SQL_STAR)
                 || strpos($columnParameters[0], $starSuffix)
             ) {
                 $selectParameters[0] = [[self::SQL_STAR]];
@@ -97,10 +87,7 @@ protected function processLimitOffset(
             $number = $this->processInfo['subselectCount'] ? $this->processInfo['subselectCount'] : '';
 
             if ($this->limit === null) {
-                array_push(
-                    $sqls,
-                    ') b ) WHERE b_rownum > (:offset' . $number . ')'
-                );
+                $sqls[] = ') b ) WHERE b_rownum > (:offset' . $number . ')';
                 $parameterContainer->offsetSet(
                     'offset' . $number,
                     $this->offset,
@@ -108,16 +95,13 @@ protected function processLimitOffset(
                 );
             } else {
                 // create bottom part of query, with offset and limit using row_number
-                array_push(
-                    $sqls,
-                    ') b WHERE rownum <= (:offset'
+                $sqls[] = ') b WHERE rownum <= (:offset'
                     . $number
                     . '+:limit'
                     . $number
                     . ')) WHERE b_rownum >= (:offset'
                     . $number
-                    . ' + 1)'
-                );
+                    . ' + 1)';
                 $parameterContainer->offsetSet(
                     'offset' . $number,
                     $this->offset,
@@ -129,21 +113,19 @@ protected function processLimitOffset(
                     $parameterContainer::TYPE_INTEGER
                 );
             }
+
             $this->processInfo['subselectCount']++;
         } else {
             if ($this->limit === null) {
-                array_push($sqls, ') b ) WHERE b_rownum > (' . (int) $this->offset . ')');
+                $sqls[] = ') b ) WHERE b_rownum > (' . (int) $this->offset . ')';
             } else {
-                array_push(
-                    $sqls,
-                    ') b WHERE rownum <= ('
+                $sqls[] = ') b WHERE rownum <= ('
                     . (int) $this->offset
                     . '+'
                     . (int) $this->limit
                     . ')) WHERE b_rownum >= ('
                     . (int) $this->offset
-                    . ' + 1)'
-                );
+                    . ' + 1)';
             }
         }
 
diff --git a/src/Sql/Platform/Platform.php b/src/Sql/Platform/Platform.php
index e702caac46..0d47d9abb4 100644
--- a/src/Sql/Platform/Platform.php
+++ b/src/Sql/Platform/Platform.php
@@ -1,42 +1,47 @@
 <?php
 /**
- * Zend Framework (http://framework.zend.com/)
- *
- * @link      http://github.com/zendframework/zf2 for the canonical source repository
- * @copyright Copyright (c) 2005-2016 Zend Technologies USA Inc. (http://www.zend.com)
- * @license   http://framework.zend.com/license/new-bsd New BSD License
+ * @see       https://github.com/zendframework/zend-db for the canonical source repository
+ * @copyright Copyright (c) 2005-2019 Zend Technologies USA Inc. (https://www.zend.com)
+ * @license   https://github.com/zendframework/zend-db/blob/master/LICENSE.md New BSD License
  */
 
+declare(strict_types=1);
+
 namespace Zend\Db\Sql\Platform;
 
 use Zend\Db\Adapter\AdapterInterface;
 use Zend\Db\Adapter\Platform\PlatformInterface;
 use Zend\Db\Adapter\StatementContainerInterface;
-use Zend\Db\Sql\Exception;
+use Zend\Db\Sql\Exception\InvalidArgumentException;
+use Zend\Db\Sql\Exception\RuntimeException;
+use Zend\Db\Sql\Platform\IbmDb2\IbmDb2;
+use Zend\Db\Sql\Platform\Mysql\Mysql;
+use Zend\Db\Sql\Platform\Oracle\Oracle;
+use Zend\Db\Sql\Platform\Sqlite\Sqlite;
+use Zend\Db\Sql\Platform\SqlServer\SqlServer;
 use Zend\Db\Sql\PreparableSqlInterface;
 use Zend\Db\Sql\SqlInterface;
+use function is_a;
+use function str_replace;
+use function strtolower;
 
 class Platform extends AbstractPlatform
 {
-    /**
-     * @var AdapterInterface
-     */
-    protected $adapter = null;
+    /** @var AdapterInterface */
+    protected $adapter;
 
-    /**
-     * @var PlatformInterface|null
-     */
+    /** @var PlatformInterface|null */
     protected $defaultPlatform;
 
     public function __construct(AdapterInterface $adapter)
     {
         $this->defaultPlatform = $adapter->getPlatform();
 
-        $mySqlPlatform     = new Mysql\Mysql();
-        $sqlServerPlatform = new SqlServer\SqlServer();
-        $oraclePlatform    = new Oracle\Oracle();
-        $ibmDb2Platform    = new IbmDb2\IbmDb2();
-        $sqlitePlatform    = new Sqlite\Sqlite();
+        $mySqlPlatform     = new Mysql();
+        $sqlServerPlatform = new SqlServer();
+        $oraclePlatform    = new Oracle();
+        $ibmDb2Platform    = new IbmDb2();
+        $sqlitePlatform    = new Sqlite();
 
         $this->decorators['mysql']     = $mySqlPlatform->getDecorators();
         $this->decorators['sqlserver'] = $sqlServerPlatform->getDecorators();
@@ -45,13 +50,11 @@ public function __construct(AdapterInterface $adapter)
         $this->decorators['sqlite']    = $sqlitePlatform->getDecorators();
     }
 
-    /**
-     * @param string                             $type
-     * @param PlatformDecoratorInterface         $decorator
-     * @param AdapterInterface|PlatformInterface $adapterOrPlatform
-     */
-    public function setTypeDecorator($type, PlatformDecoratorInterface $decorator, $adapterOrPlatform = null)
-    {
+    public function setTypeDecorator(
+        string                     $type,
+        PlatformDecoratorInterface $decorator,
+        $adapterOrPlatform = null
+    ) : void {
         $platformName = $this->resolvePlatformName($adapterOrPlatform);
         $this->decorators[$platformName][$type] = $decorator;
     }
@@ -69,6 +72,7 @@ public function getTypeDecorator($subject, $adapterOrPlatform = null)
             foreach ($this->decorators[$platformName] as $type => $decorator) {
                 if ($subject instanceof $type && is_a($decorator, $type, true)) {
                     $decorator->setSubject($subject);
+
                     return $decorator;
                 }
             }
@@ -78,23 +82,19 @@ public function getTypeDecorator($subject, $adapterOrPlatform = null)
     }
 
     /**
-     * @return array|PlatformDecoratorInterface[]
+     * @return array|PlatformDecoratorInterface
      */
     public function getDecorators()
     {
         $platformName = $this->resolvePlatformName($this->getDefaultPlatform());
+
         return $this->decorators[$platformName];
     }
 
-    /**
-     * {@inheritDoc}
-     *
-     * @throws Exception\RuntimeException
-     */
     public function prepareStatement(AdapterInterface $adapter, StatementContainerInterface $statementContainer)
     {
         if (! $this->subject instanceof PreparableSqlInterface) {
-            throw new Exception\RuntimeException(
+            throw new RuntimeException(
                 'The subject does not appear to implement Zend\Db\Sql\PreparableSqlInterface, thus calling '
                 . 'prepareStatement() has no effect'
             );
@@ -105,15 +105,10 @@ public function prepareStatement(AdapterInterface $adapter, StatementContainerIn
         return $statementContainer;
     }
 
-    /**
-     * {@inheritDoc}
-     *
-     * @throws Exception\RuntimeException
-     */
-    public function getSqlString(PlatformInterface $adapterPlatform = null)
+    public function getSqlString(?PlatformInterface $adapterPlatform = null) : string
     {
         if (! $this->subject instanceof SqlInterface) {
-            throw new Exception\RuntimeException(
+            throw new RuntimeException(
                 'The subject does not appear to implement Zend\Db\Sql\SqlInterface, thus calling '
                 . 'prepareStatement() has no effect'
             );
@@ -127,16 +122,15 @@ public function getSqlString(PlatformInterface $adapterPlatform = null)
     protected function resolvePlatformName($adapterOrPlatform)
     {
         $platformName = $this->resolvePlatform($adapterOrPlatform)->getName();
+
         return str_replace([' ', '_'], '', strtolower($platformName));
     }
     /**
      * @param null|PlatformInterface|AdapterInterface $adapterOrPlatform
-     *
      * @return PlatformInterface
-     *
-     * @throws Exception\InvalidArgumentException
+     * @throws InvalidArgumentException
      */
-    protected function resolvePlatform($adapterOrPlatform)
+    protected function resolvePlatform($adapterOrPlatform) : PlatformInterface
     {
         if (! $adapterOrPlatform) {
             return $this->getDefaultPlatform();
@@ -150,22 +144,21 @@ protected function resolvePlatform($adapterOrPlatform)
             return $adapterOrPlatform;
         }
 
-        throw new Exception\InvalidArgumentException(sprintf(
+        throw new InvalidArgumentException(sprintf(
             '$adapterOrPlatform should be null, %s, or %s',
-            'Zend\Db\Adapter\AdapterInterface',
-            'Zend\Db\Adapter\Platform\PlatformInterface'
+            AdapterInterface::class,
+            PlatformInterface::class
         ));
     }
 
     /**
      * @return PlatformInterface
-     *
-     * @throws Exception\RuntimeException
+     * @throws RuntimeException
      */
-    protected function getDefaultPlatform()
+    protected function getDefaultPlatform() : PlatformInterface
     {
         if (! $this->defaultPlatform) {
-            throw new Exception\RuntimeException('$this->defaultPlatform was not set');
+            throw new RuntimeException('$this->defaultPlatform was not set');
         }
 
         return $this->defaultPlatform;
diff --git a/src/Sql/Platform/PlatformDecoratorInterface.php b/src/Sql/Platform/PlatformDecoratorInterface.php
index f06c4340d2..4bf490a6f7 100644
--- a/src/Sql/Platform/PlatformDecoratorInterface.php
+++ b/src/Sql/Platform/PlatformDecoratorInterface.php
@@ -1,19 +1,18 @@
 <?php
 /**
- * Zend Framework (http://framework.zend.com/)
- *
- * @link      http://github.com/zendframework/zf2 for the canonical source repository
- * @copyright Copyright (c) 2005-2016 Zend Technologies USA Inc. (http://www.zend.com)
- * @license   http://framework.zend.com/license/new-bsd New BSD License
+ * @see       https://github.com/zendframework/zend-db for the canonical source repository
+ * @copyright Copyright (c) 2005-2019 Zend Technologies USA Inc. (https://www.zend.com)
+ * @license   https://github.com/zendframework/zend-db/blob/master/LICENSE.md New BSD License
  */
 
+declare(strict_types=1);
+
 namespace Zend\Db\Sql\Platform;
 
 interface PlatformDecoratorInterface
 {
     /**
      * @param $subject
-     *
      * @return self
      */
     public function setSubject($subject);
diff --git a/src/Sql/Platform/SqlServer/Ddl/CreateTableDecorator.php b/src/Sql/Platform/SqlServer/Ddl/CreateTableDecorator.php
index 0618682b26..dc91af6ada 100644
--- a/src/Sql/Platform/SqlServer/Ddl/CreateTableDecorator.php
+++ b/src/Sql/Platform/SqlServer/Ddl/CreateTableDecorator.php
@@ -1,12 +1,12 @@
 <?php
 /**
- * Zend Framework (http://framework.zend.com/)
- *
- * @link      http://github.com/zendframework/zf2 for the canonical source repository
- * @copyright Copyright (c) 2005-2016 Zend Technologies USA Inc. (http://www.zend.com)
- * @license   http://framework.zend.com/license/new-bsd New BSD License
+ * @see       https://github.com/zendframework/zend-db for the canonical source repository
+ * @copyright Copyright (c) 2005-2019 Zend Technologies USA Inc. (https://www.zend.com)
+ * @license   https://github.com/zendframework/zend-db/blob/master/LICENSE.md New BSD License
  */
 
+declare(strict_types=1);
+
 namespace Zend\Db\Sql\Platform\SqlServer\Ddl;
 
 use Zend\Db\Adapter\Platform\PlatformInterface;
@@ -15,28 +15,24 @@
 
 class CreateTableDecorator extends CreateTable implements PlatformDecoratorInterface
 {
-    /**
-     * @var CreateTable
-     */
+    /** @var CreateTable */
     protected $subject;
 
     /**
      * @param CreateTable $subject
-     * @return self Provides a fluent interface
+     * @return $this
      */
-    public function setSubject($subject)
+    public function setSubject($subject) : self
     {
         $this->subject = $subject;
+
         return $this;
     }
 
-    /**
-     * @param PlatformInterface $adapterPlatform
-     * @return array
-     */
-    protected function processTable(PlatformInterface $adapterPlatform = null)
+    protected function processTable(?PlatformInterface $adapterPlatform = null) : array
     {
         $table = ($this->isTemporary ? '#' : '') . ltrim($this->table, '#');
+
         return [
             '',
             $adapterPlatform->quoteIdentifier($table),
diff --git a/src/Sql/Platform/SqlServer/SelectDecorator.php b/src/Sql/Platform/SqlServer/SelectDecorator.php
index 642d10b563..afd2adac74 100644
--- a/src/Sql/Platform/SqlServer/SelectDecorator.php
+++ b/src/Sql/Platform/SqlServer/SelectDecorator.php
@@ -1,12 +1,12 @@
 <?php
 /**
- * Zend Framework (http://framework.zend.com/)
- *
- * @link      http://github.com/zendframework/zf2 for the canonical source repository
- * @copyright Copyright (c) 2005-2016 Zend Technologies USA Inc. (http://www.zend.com)
- * @license   http://framework.zend.com/license/new-bsd New BSD License
+ * @see       https://github.com/zendframework/zend-db for the canonical source repository
+ * @copyright Copyright (c) 2005-2019 Zend Technologies USA Inc. (https://www.zend.com)
+ * @license   https://github.com/zendframework/zend-db/blob/master/LICENSE.md New BSD License
  */
 
+declare(strict_types=1);
+
 namespace Zend\Db\Sql\Platform\SqlServer;
 
 use Zend\Db\Adapter\Driver\DriverInterface;
@@ -14,13 +14,16 @@
 use Zend\Db\Adapter\Platform\PlatformInterface;
 use Zend\Db\Sql\Platform\PlatformDecoratorInterface;
 use Zend\Db\Sql\Select;
+use function array_shift;
+use function array_unshift;
+use function array_values;
+use function current;
+use function strpos;
 
 class SelectDecorator extends Select implements PlatformDecoratorInterface
 {
-    /**
-     * @var Select
-     */
-    protected $subject = null;
+    /** @var Select */
+    protected $subject;
 
     /**
      * @param Select $select
@@ -30,7 +33,7 @@ public function setSubject($select)
         $this->subject = $select;
     }
 
-    protected function localizeVariables()
+    protected function localizeVariables() : void
     {
         parent::localizeVariables();
         // set specifications
@@ -40,21 +43,13 @@ protected function localizeVariables()
         $this->specifications['LIMITOFFSET'] = null;
     }
 
-    /**
-     * @param PlatformInterface $platform
-     * @param DriverInterface $driver
-     * @param ParameterContainer $parameterContainer
-     * @param $sqls
-     * @param $parameters
-     * @return null
-     */
     protected function processLimitOffset(
-        PlatformInterface $platform,
-        DriverInterface $driver = null,
-        ParameterContainer $parameterContainer = null,
+        PlatformInterface   $platform,
+        ?DriverInterface    $driver = null,
+        ?ParameterContainer $parameterContainer = null,
         &$sqls,
         &$parameters
-    ) {
+    ) : void {
         if ($this->limit === null && $this->offset === null) {
             return;
         }
@@ -71,8 +66,8 @@ protected function processLimitOffset(
 
         $starSuffix = $platform->getIdentifierSeparator() . self::SQL_STAR;
         foreach ($selectParameters[0] as $i => $columnParameters) {
-            if ($columnParameters[0] == self::SQL_STAR
-                || (isset($columnParameters[1]) && $columnParameters[1] == self::SQL_STAR)
+            if ($columnParameters[0] === self::SQL_STAR
+                || (isset($columnParameters[1]) && $columnParameters[1] === self::SQL_STAR)
                 || strpos($columnParameters[0], $starSuffix)
             ) {
                 $selectParameters[0] = [[self::SQL_STAR]];
@@ -96,17 +91,17 @@ protected function processLimitOffset(
             $offsetParamName = $driver->formatParameterName('offset');
             $offsetForSumParamName = $driver->formatParameterName('offsetForSum');
             // @codingStandardsIgnoreStart
-            array_push($sqls, ') AS [ZEND_SQL_SERVER_LIMIT_OFFSET_EMULATION] WHERE [ZEND_SQL_SERVER_LIMIT_OFFSET_EMULATION].[__ZEND_ROW_NUMBER] BETWEEN '
-                . $offsetParamName . '+1 AND ' . $limitParamName . '+' . $offsetForSumParamName);
+            $sqls[] = ') AS [ZEND_SQL_SERVER_LIMIT_OFFSET_EMULATION] WHERE [ZEND_SQL_SERVER_LIMIT_OFFSET_EMULATION].[__ZEND_ROW_NUMBER] BETWEEN '
+                . $offsetParamName . '+1 AND ' . $limitParamName . '+' . $offsetForSumParamName;
             // @codingStandardsIgnoreEnd
             $parameterContainer->offsetSet('offset', $this->offset);
             $parameterContainer->offsetSet('limit', $this->limit);
             $parameterContainer->offsetSetReference('offsetForSum', 'offset');
         } else {
             // @codingStandardsIgnoreStart
-            array_push($sqls, ') AS [ZEND_SQL_SERVER_LIMIT_OFFSET_EMULATION] WHERE [ZEND_SQL_SERVER_LIMIT_OFFSET_EMULATION].[__ZEND_ROW_NUMBER] BETWEEN '
+            $sqls[] = ') AS [ZEND_SQL_SERVER_LIMIT_OFFSET_EMULATION] WHERE [ZEND_SQL_SERVER_LIMIT_OFFSET_EMULATION].[__ZEND_ROW_NUMBER] BETWEEN '
                 . (int) $this->offset . '+1 AND '
-                . (int) $this->limit . '+' . (int) $this->offset);
+                . (int) $this->limit . '+' . (int) $this->offset;
             // @codingStandardsIgnoreEnd
         }
 
diff --git a/src/Sql/Platform/SqlServer/SqlServer.php b/src/Sql/Platform/SqlServer/SqlServer.php
index 0dc383d0be..94539f201d 100644
--- a/src/Sql/Platform/SqlServer/SqlServer.php
+++ b/src/Sql/Platform/SqlServer/SqlServer.php
@@ -1,21 +1,24 @@
 <?php
 /**
- * Zend Framework (http://framework.zend.com/)
- *
- * @link      http://github.com/zendframework/zf2 for the canonical source repository
- * @copyright Copyright (c) 2005-2016 Zend Technologies USA Inc. (http://www.zend.com)
- * @license   http://framework.zend.com/license/new-bsd New BSD License
+ * @see       https://github.com/zendframework/zend-db for the canonical source repository
+ * @copyright Copyright (c) 2005-2019 Zend Technologies USA Inc. (https://www.zend.com)
+ * @license   https://github.com/zendframework/zend-db/blob/master/LICENSE.md New BSD License
  */
 
+declare(strict_types=1);
+
 namespace Zend\Db\Sql\Platform\SqlServer;
 
+use Zend\Db\Sql\Ddl\CreateTable;
 use Zend\Db\Sql\Platform\AbstractPlatform;
+use Zend\Db\Sql\Platform\SqlServer\Ddl\CreateTableDecorator;
+use Zend\Db\Sql\Select;
 
 class SqlServer extends AbstractPlatform
 {
-    public function __construct(SelectDecorator $selectDecorator = null)
+    public function __construct(?SelectDecorator $selectDecorator = null)
     {
-        $this->setTypeDecorator('Zend\Db\Sql\Select', ($selectDecorator) ?: new SelectDecorator());
-        $this->setTypeDecorator('Zend\Db\Sql\Ddl\CreateTable', new Ddl\CreateTableDecorator());
+        $this->setTypeDecorator(Select::class, $selectDecorator ?? new SelectDecorator());
+        $this->setTypeDecorator(CreateTable::class, new CreateTableDecorator());
     }
 }
diff --git a/src/Sql/Platform/Sqlite/SelectDecorator.php b/src/Sql/Platform/Sqlite/SelectDecorator.php
index a1b3d6c508..9a1a5c88c6 100644
--- a/src/Sql/Platform/Sqlite/SelectDecorator.php
+++ b/src/Sql/Platform/Sqlite/SelectDecorator.php
@@ -1,12 +1,12 @@
 <?php
 /**
- * Zend Framework (http://framework.zend.com/)
- *
- * @link      http://github.com/zendframework/zf2 for the canonical source repository
- * @copyright Copyright (c) 2005-2015 Zend Technologies USA Inc. (http://www.zend.com)
- * @license   http://framework.zend.com/license/new-bsd New BSD License
+ * @see       https://github.com/zendframework/zend-db for the canonical source repository
+ * @copyright Copyright (c) 2005-2019 Zend Technologies USA Inc. (https://www.zend.com)
+ * @license   https://github.com/zendframework/zend-db/blob/master/LICENSE.md New BSD License
  */
 
+declare(strict_types=1);
+
 namespace Zend\Db\Sql\Platform\Sqlite;
 
 use Zend\Db\Adapter\Driver\DriverInterface;
@@ -17,58 +17,51 @@
 
 class SelectDecorator extends Select implements PlatformDecoratorInterface
 {
-    /**
-     * @var Select
-     */
-    protected $subject = null;
+    /** @var Select */
+    protected $subject;
 
     /**
-     * Set Subject
-     *
      * @param Select $select
-     * @return self Provides a fluent interface
+     * @return $this
      */
-    public function setSubject($select)
+    public function setSubject($select) : self
     {
         $this->subject = $select;
 
         return $this;
     }
 
-    /**
-     * {@inheritDoc}
-     */
-    protected function localizeVariables()
+    protected function localizeVariables() : void
     {
         parent::localizeVariables();
         $this->specifications[self::COMBINE] = '%1$s %2$s';
     }
 
-    /**
-     * {@inheritDoc}
-     */
     protected function processStatementStart(
-        PlatformInterface $platform,
-        DriverInterface $driver = null,
-        ParameterContainer $parameterContainer = null
-    ) {
-        return '';
+        PlatformInterface   $platform,
+        ?DriverInterface    $driver = null,
+        ?ParameterContainer $parameterContainer = null
+    ) : array {
+        return [];
     }
 
     protected function processLimit(
-        PlatformInterface $platform,
-        DriverInterface $driver = null,
-        ParameterContainer $parameterContainer = null
+        PlatformInterface   $platform,
+        ?DriverInterface    $driver = null,
+        ?ParameterContainer $parameterContainer = null
     ) {
         if ($this->limit === null && $this->offset !== null) {
             return [''];
         }
+
         if ($this->limit === null) {
             return;
         }
+
         if ($parameterContainer) {
             $paramPrefix = $this->processInfo['paramPrefix'];
             $parameterContainer->offsetSet($paramPrefix . 'limit', $this->limit, ParameterContainer::TYPE_INTEGER);
+
             return [$driver->formatParameterName('limit')];
         }
 
@@ -76,9 +69,9 @@ protected function processLimit(
     }
 
     protected function processOffset(
-        PlatformInterface $platform,
-        DriverInterface $driver = null,
-        ParameterContainer $parameterContainer = null
+        PlatformInterface   $platform,
+        ?DriverInterface    $driver = null,
+        ?ParameterContainer $parameterContainer = null
     ) {
         if ($this->offset === null) {
             return;
@@ -92,14 +85,11 @@ protected function processOffset(
         return [$this->offset];
     }
 
-    /**
-     * {@inheritDoc}
-     */
     protected function processStatementEnd(
-        PlatformInterface $platform,
-        DriverInterface $driver = null,
-        ParameterContainer $parameterContainer = null
-    ) {
-        return '';
+        PlatformInterface   $platform,
+        ?DriverInterface    $driver = null,
+        ?ParameterContainer $parameterContainer = null
+    ) : array {
+        return [];
     }
 }
diff --git a/src/Sql/Platform/Sqlite/Sqlite.php b/src/Sql/Platform/Sqlite/Sqlite.php
index 00712dded1..bdda4d5fa6 100644
--- a/src/Sql/Platform/Sqlite/Sqlite.php
+++ b/src/Sql/Platform/Sqlite/Sqlite.php
@@ -1,25 +1,21 @@
 <?php
 /**
- * Zend Framework (http://framework.zend.com/)
- *
- * @link      http://github.com/zendframework/zf2 for the canonical source repository
- * @copyright Copyright (c) 2005-2015 Zend Technologies USA Inc. (http://www.zend.com)
- * @license   http://framework.zend.com/license/new-bsd New BSD License
+ * @see       https://github.com/zendframework/zend-db for the canonical source repository
+ * @copyright Copyright (c) 2005-2019 Zend Technologies USA Inc. (https://www.zend.com)
+ * @license   https://github.com/zendframework/zend-db/blob/master/LICENSE.md New BSD License
  */
 
+declare(strict_types=1);
+
 namespace Zend\Db\Sql\Platform\Sqlite;
 
 use Zend\Db\Sql\Platform\AbstractPlatform;
+use Zend\Db\Sql\Select;
 
 class Sqlite extends AbstractPlatform
 {
-    /**
-     * Constructor
-     *
-     * Registers the type decorator.
-     */
     public function __construct()
     {
-        $this->setTypeDecorator('Zend\Db\Sql\Select', new SelectDecorator());
+        $this->setTypeDecorator(Select::class, new SelectDecorator());
     }
 }
diff --git a/src/Sql/Predicate/Between.php b/src/Sql/Predicate/Between.php
index 4b1545eb08..efc0cb4f2c 100644
--- a/src/Sql/Predicate/Between.php
+++ b/src/Sql/Predicate/Between.php
@@ -1,12 +1,12 @@
 <?php
 /**
- * Zend Framework (http://framework.zend.com/)
- *
- * @link      http://github.com/zendframework/zf2 for the canonical source repository
- * @copyright Copyright (c) 2005-2016 Zend Technologies USA Inc. (http://www.zend.com)
- * @license   http://framework.zend.com/license/new-bsd New BSD License
+ * @see       https://github.com/zendframework/zend-db for the canonical source repository
+ * @copyright Copyright (c) 2005-2019 Zend Technologies USA Inc. (https://www.zend.com)
+ * @license   https://github.com/zendframework/zend-db/blob/master/LICENSE.md New BSD License
  */
 
+declare(strict_types=1);
+
 namespace Zend\Db\Sql\Predicate;
 
 use Zend\Db\Sql\AbstractExpression;
@@ -14,48 +14,40 @@
 class Between extends AbstractExpression implements PredicateInterface
 {
     protected $specification = '%1$s BETWEEN %2$s AND %3$s';
-    protected $identifier    = null;
-    protected $minValue      = null;
-    protected $maxValue      = null;
+    protected $identifier;
+    protected $minValue;
+    protected $maxValue;
 
     /**
      * Constructor
      *
-     * @param  string $identifier
-     * @param  int|float|string $minValue
-     * @param  int|float|string $maxValue
+     * @param null|string           $identifier
+     * @param null|int|float|string $minValue
+     * @param null|int|float|string $maxValue
      */
-    public function __construct($identifier = null, $minValue = null, $maxValue = null)
+    public function __construct(?string $identifier = null, $minValue = null, $maxValue = null)
     {
         if ($identifier) {
             $this->setIdentifier($identifier);
         }
+
         if ($minValue !== null) {
             $this->setMinValue($minValue);
         }
+
         if ($maxValue !== null) {
             $this->setMaxValue($maxValue);
         }
     }
 
-    /**
-     * Set identifier for comparison
-     *
-     * @param  string $identifier
-     * @return self Provides a fluent interface
-     */
-    public function setIdentifier($identifier)
+    public function setIdentifier(string $identifier) : self
     {
         $this->identifier = $identifier;
+
         return $this;
     }
 
-    /**
-     * Get identifier of comparison
-     *
-     * @return null|string
-     */
-    public function getIdentifier()
+    public function getIdentifier() : ?string
     {
         return $this->identifier;
     }
@@ -63,12 +55,13 @@ public function getIdentifier()
     /**
      * Set minimum boundary for comparison
      *
-     * @param  int|float|string $minValue
-     * @return self Provides a fluent interface
+     * @param int|float|string $minValue
+     * @return $this
      */
-    public function setMinValue($minValue)
+    public function setMinValue($minValue) : self
     {
         $this->minValue = $minValue;
+
         return $this;
     }
 
@@ -85,12 +78,13 @@ public function getMinValue()
     /**
      * Set maximum boundary for comparison
      *
-     * @param  int|float|string $maxValue
-     * @return self Provides a fluent interface
+     * @param int|float|string $maxValue
+     * @return $this
      */
-    public function setMaxValue($maxValue)
+    public function setMaxValue($maxValue) : self
     {
         $this->maxValue = $maxValue;
+
         return $this;
     }
 
@@ -104,34 +98,19 @@ public function getMaxValue()
         return $this->maxValue;
     }
 
-    /**
-     * Set specification string to use in forming SQL predicate
-     *
-     * @param  string $specification
-     * @return self Provides a fluent interface
-     */
-    public function setSpecification($specification)
+    public function setSpecification(string $specification) : self
     {
         $this->specification = $specification;
+
         return $this;
     }
 
-    /**
-     * Get specification string to use in forming SQL predicate
-     *
-     * @return string
-     */
-    public function getSpecification()
+    public function getSpecification() : string
     {
         return $this->specification;
     }
 
-    /**
-     * Return "where" parts
-     *
-     * @return array
-     */
-    public function getExpressionData()
+    public function getExpressionData() : array
     {
         list($values[], $types[]) = $this->normalizeArgument($this->identifier, self::TYPE_IDENTIFIER);
         list($values[], $types[]) = $this->normalizeArgument($this->minValue, self::TYPE_VALUE);
diff --git a/src/Sql/Predicate/Expression.php b/src/Sql/Predicate/Expression.php
index e9b5363f24..5694c4aebe 100644
--- a/src/Sql/Predicate/Expression.php
+++ b/src/Sql/Predicate/Expression.php
@@ -1,25 +1,22 @@
 <?php
 /**
- * Zend Framework (http://framework.zend.com/)
- *
- * @link      http://github.com/zendframework/zf2 for the canonical source repository
- * @copyright Copyright (c) 2005-2016 Zend Technologies USA Inc. (http://www.zend.com)
- * @license   http://framework.zend.com/license/new-bsd New BSD License
+ * @see       https://github.com/zendframework/zend-db for the canonical source repository
+ * @copyright Copyright (c) 2005-2019 Zend Technologies USA Inc. (https://www.zend.com)
+ * @license   https://github.com/zendframework/zend-db/blob/master/LICENSE.md New BSD License
  */
 
+declare(strict_types=1);
+
 namespace Zend\Db\Sql\Predicate;
 
 use Zend\Db\Sql\Expression as BaseExpression;
+use function array_slice;
+use function func_get_args;
+use function is_array;
 
 class Expression extends BaseExpression implements PredicateInterface
 {
-    /**
-     * Constructor
-     *
-     * @param string $expression
-     * @param int|float|bool|string|array $valueParameter
-     */
-    public function __construct($expression = null, $valueParameter = null /*[, $valueParameter, ... ]*/)
+    public function __construct(?string $expression = null, $valueParameter = null)
     {
         if ($expression) {
             $this->setExpression($expression);
diff --git a/src/Sql/Predicate/In.php b/src/Sql/Predicate/In.php
index 0c62189cf0..a312d7cb2a 100644
--- a/src/Sql/Predicate/In.php
+++ b/src/Sql/Predicate/In.php
@@ -1,17 +1,23 @@
 <?php
 /**
- * Zend Framework (http://framework.zend.com/)
- *
- * @link      http://github.com/zendframework/zf2 for the canonical source repository
- * @copyright Copyright (c) 2005-2016 Zend Technologies USA Inc. (http://www.zend.com)
- * @license   http://framework.zend.com/license/new-bsd New BSD License
+ * @see       https://github.com/zendframework/zend-db for the canonical source repository
+ * @copyright Copyright (c) 2005-2019 Zend Technologies USA Inc. (https://www.zend.com)
+ * @license   https://github.com/zendframework/zend-db/blob/master/LICENSE.md New BSD License
  */
 
+declare(strict_types=1);
+
 namespace Zend\Db\Sql\Predicate;
 
+use Zend\Db\Sql\AbstractExpression;
 use Zend\Db\Sql\Exception;
 use Zend\Db\Sql\Select;
-use Zend\Db\Sql\AbstractExpression;
+use function array_fill;
+use function count;
+use function gettype;
+use function implode;
+use function is_array;
+use function vsprintf;
 
 class In extends AbstractExpression implements PredicateInterface
 {
@@ -33,6 +39,7 @@ public function __construct($identifier = null, $valueSet = null)
         if ($identifier) {
             $this->setIdentifier($identifier);
         }
+
         if ($valueSet !== null) {
             $this->setValueSet($valueSet);
         }
@@ -41,10 +48,10 @@ public function __construct($identifier = null, $valueSet = null)
     /**
      * Set identifier for comparison
      *
-     * @param  string|array $identifier
-     * @return self Provides a fluent interface
+     * @param string|array $identifier
+     * @return $this
      */
-    public function setIdentifier($identifier)
+    public function setIdentifier($identifier) : self
     {
         $this->identifier = $identifier;
 
@@ -64,17 +71,19 @@ public function getIdentifier()
     /**
      * Set set of values for IN comparison
      *
-     * @param  array|Select                       $valueSet
-     * @return self Provides a fluent interface
+     * @param array|Select $valueSet
+     * @return $this
+     *
      * @throws Exception\InvalidArgumentException
      */
-    public function setValueSet($valueSet)
+    public function setValueSet($valueSet) : self
     {
         if (! is_array($valueSet) && ! $valueSet instanceof Select) {
             throw new Exception\InvalidArgumentException(
                 '$valueSet must be either an array or a Zend\Db\Sql\Select object, ' . gettype($valueSet) . ' given'
             );
         }
+
         $this->valueSet = $valueSet;
 
         return $this;
@@ -82,7 +91,6 @@ public function setValueSet($valueSet)
 
     /**
      * Gets set of values in IN comparison
-     *
      * @return array|Select
      */
     public function getValueSet()
@@ -90,12 +98,7 @@ public function getValueSet()
         return $this->valueSet;
     }
 
-    /**
-     * Return array of parts for where statement
-     *
-     * @return array
-     */
-    public function getExpressionData()
+    public function getExpressionData() : array
     {
         $identifier = $this->getIdentifier();
         $values = $this->getValueSet();
diff --git a/src/Sql/Predicate/IsNotNull.php b/src/Sql/Predicate/IsNotNull.php
index e42c9aa5b5..ebbe99269c 100644
--- a/src/Sql/Predicate/IsNotNull.php
+++ b/src/Sql/Predicate/IsNotNull.php
@@ -1,12 +1,12 @@
 <?php
 /**
- * Zend Framework (http://framework.zend.com/)
- *
- * @link      http://github.com/zendframework/zf2 for the canonical source repository
- * @copyright Copyright (c) 2005-2016 Zend Technologies USA Inc. (http://www.zend.com)
- * @license   http://framework.zend.com/license/new-bsd New BSD License
+ * @see       https://github.com/zendframework/zend-db for the canonical source repository
+ * @copyright Copyright (c) 2005-2019 Zend Technologies USA Inc. (https://www.zend.com)
+ * @license   https://github.com/zendframework/zend-db/blob/master/LICENSE.md New BSD License
  */
 
+declare(strict_types=1);
+
 namespace Zend\Db\Sql\Predicate;
 
 class IsNotNull extends IsNull
diff --git a/src/Sql/Predicate/IsNull.php b/src/Sql/Predicate/IsNull.php
index daf45f3c55..84b1ce95e7 100644
--- a/src/Sql/Predicate/IsNull.php
+++ b/src/Sql/Predicate/IsNull.php
@@ -1,90 +1,56 @@
 <?php
 /**
- * Zend Framework (http://framework.zend.com/)
- *
- * @link      http://github.com/zendframework/zf2 for the canonical source repository
- * @copyright Copyright (c) 2005-2016 Zend Technologies USA Inc. (http://www.zend.com)
- * @license   http://framework.zend.com/license/new-bsd New BSD License
+ * @see       https://github.com/zendframework/zend-db for the canonical source repository
+ * @copyright Copyright (c) 2005-2019 Zend Technologies USA Inc. (https://www.zend.com)
+ * @license   https://github.com/zendframework/zend-db/blob/master/LICENSE.md New BSD License
  */
 
+declare(strict_types=1);
+
 namespace Zend\Db\Sql\Predicate;
 
 use Zend\Db\Sql\AbstractExpression;
 
 class IsNull extends AbstractExpression implements PredicateInterface
 {
-    /**
-     * @var string
-     */
+    /** @var string */
     protected $specification = '%1$s IS NULL';
 
-    /**
-     * @var
-     */
+    /** @var null|string */
     protected $identifier;
 
-    /**
-     * Constructor
-     *
-     * @param  string $identifier
-     */
-    public function __construct($identifier = null)
+    public function __construct(?string $identifier = null)
     {
         if ($identifier) {
             $this->setIdentifier($identifier);
         }
     }
 
-    /**
-     * Set identifier for comparison
-     *
-     * @param  string $identifier
-     * @return self Provides a fluent interface
-     */
-    public function setIdentifier($identifier)
+    public function setIdentifier(string $identifier) : self
     {
         $this->identifier = $identifier;
+
         return $this;
     }
 
-    /**
-     * Get identifier of comparison
-     *
-     * @return null|string
-     */
-    public function getIdentifier()
+    public function getIdentifier() : ?string
     {
         return $this->identifier;
     }
 
-    /**
-     * Set specification string to use in forming SQL predicate
-     *
-     * @param  string $specification
-     * @return self Provides a fluent interface
-     */
-    public function setSpecification($specification)
+    public function setSpecification(string $specification) : self
     {
         $this->specification = $specification;
+
         return $this;
     }
 
-    /**
-     * Get specification string to use in forming SQL predicate
-     *
-     * @return string
-     */
-    public function getSpecification()
+    public function getSpecification() : string
     {
         return $this->specification;
     }
 
-    /**
-     * Get parts for where statement
-     *
-     * @return array
-     */
-    public function getExpressionData()
+    public function getExpressionData() : array
     {
         $identifier = $this->normalizeArgument($this->identifier, self::TYPE_IDENTIFIER);
         return [[
diff --git a/src/Sql/Predicate/Like.php b/src/Sql/Predicate/Like.php
index 2f1ffde79b..72905996e3 100644
--- a/src/Sql/Predicate/Like.php
+++ b/src/Sql/Predicate/Like.php
@@ -1,108 +1,79 @@
 <?php
 /**
- * Zend Framework (http://framework.zend.com/)
- *
- * @link      http://github.com/zendframework/zf2 for the canonical source repository
- * @copyright Copyright (c) 2005-2016 Zend Technologies USA Inc. (http://www.zend.com)
- * @license   http://framework.zend.com/license/new-bsd New BSD License
+ * @see       https://github.com/zendframework/zend-db for the canonical source repository
+ * @copyright Copyright (c) 2005-2019 Zend Technologies USA Inc. (https://www.zend.com)
+ * @license   https://github.com/zendframework/zend-db/blob/master/LICENSE.md New BSD License
  */
 
+declare(strict_types=1);
+
 namespace Zend\Db\Sql\Predicate;
 
 use Zend\Db\Sql\AbstractExpression;
 
 class Like extends AbstractExpression implements PredicateInterface
 {
-    /**
-     * @var string
-     */
+    /** @var string */
     protected $specification = '%1$s LIKE %2$s';
 
-    /**
-     * @var string
-     */
+    /** @var string */
     protected $identifier = '';
 
-    /**
-     * @var string
-     */
+    /** @var string */
     protected $like = '';
 
-    /**
-     * @param string $identifier
-     * @param string $like
-     */
-    public function __construct($identifier = null, $like = null)
+    public function __construct(?string $identifier = null, ?string $like = null)
     {
         if ($identifier) {
             $this->setIdentifier($identifier);
         }
+
         if ($like) {
             $this->setLike($like);
         }
     }
 
-    /**
-     * @param  string $identifier
-     * @return self Provides a fluent interface
-     */
-    public function setIdentifier($identifier)
+    public function setIdentifier(string $identifier) : self
     {
         $this->identifier = $identifier;
+
         return $this;
     }
 
-    /**
-     * @return string
-     */
-    public function getIdentifier()
+    public function getIdentifier() : string
     {
         return $this->identifier;
     }
 
-    /**
-     * @param  string $like
-     * @return self Provides a fluent interface
-     */
-    public function setLike($like)
+    public function setLike(string $like) : self
     {
         $this->like = $like;
+
         return $this;
     }
 
-    /**
-     * @return string
-     */
-    public function getLike()
+    public function getLike() : string
     {
         return $this->like;
     }
 
-    /**
-     * @param  string $specification
-     * @return self Provides a fluent interface
-     */
-    public function setSpecification($specification)
+    public function setSpecification(string $specification) : self
     {
         $this->specification = $specification;
+
         return $this;
     }
 
-    /**
-     * @return string
-     */
-    public function getSpecification()
+    public function getSpecification() : string
     {
         return $this->specification;
     }
 
-    /**
-     * @return array
-     */
-    public function getExpressionData()
+    public function getExpressionData() : array
     {
         list($values[], $types[]) = $this->normalizeArgument($this->identifier, self::TYPE_IDENTIFIER);
         list($values[], $types[]) = $this->normalizeArgument($this->like, self::TYPE_VALUE);
+
         return [
             [
                 $this->specification,
diff --git a/src/Sql/Predicate/Literal.php b/src/Sql/Predicate/Literal.php
index d4b509fc93..fa18a887c8 100644
--- a/src/Sql/Predicate/Literal.php
+++ b/src/Sql/Predicate/Literal.php
@@ -1,12 +1,12 @@
 <?php
 /**
- * Zend Framework (http://framework.zend.com/)
- *
- * @link      http://github.com/zendframework/zf2 for the canonical source repository
- * @copyright Copyright (c) 2005-2016 Zend Technologies USA Inc. (http://www.zend.com)
- * @license   http://framework.zend.com/license/new-bsd New BSD License
+ * @see       https://github.com/zendframework/zend-db for the canonical source repository
+ * @copyright Copyright (c) 2005-2019 Zend Technologies USA Inc. (https://www.zend.com)
+ * @license   https://github.com/zendframework/zend-db/blob/master/LICENSE.md New BSD License
  */
 
+declare(strict_types=1);
+
 namespace Zend\Db\Sql\Predicate;
 
 use Zend\Db\Sql\Literal as BaseLiteral;
diff --git a/src/Sql/Predicate/NotBetween.php b/src/Sql/Predicate/NotBetween.php
index a448a77e69..120449581c 100644
--- a/src/Sql/Predicate/NotBetween.php
+++ b/src/Sql/Predicate/NotBetween.php
@@ -1,15 +1,16 @@
 <?php
 /**
- * Zend Framework (http://framework.zend.com/)
- *
- * @link      http://github.com/zendframework/zf2 for the canonical source repository
- * @copyright Copyright (c) 2005-2016 Zend Technologies USA Inc. (http://www.zend.com)
- * @license   http://framework.zend.com/license/new-bsd New BSD License
+ * @see       https://github.com/zendframework/zend-db for the canonical source repository
+ * @copyright Copyright (c) 2005-2019 Zend Technologies USA Inc. (https://www.zend.com)
+ * @license   https://github.com/zendframework/zend-db/blob/master/LICENSE.md New BSD License
  */
 
+declare(strict_types=1);
+
 namespace Zend\Db\Sql\Predicate;
 
 class NotBetween extends Between
 {
+    /** @var string */
     protected $specification = '%1$s NOT BETWEEN %2$s AND %3$s';
 }
diff --git a/src/Sql/Predicate/NotIn.php b/src/Sql/Predicate/NotIn.php
index f1ce87c235..72477ad655 100644
--- a/src/Sql/Predicate/NotIn.php
+++ b/src/Sql/Predicate/NotIn.php
@@ -1,15 +1,16 @@
 <?php
 /**
- * Zend Framework (http://framework.zend.com/)
- *
- * @link      http://github.com/zendframework/zf2 for the canonical source repository
- * @copyright Copyright (c) 2005-2016 Zend Technologies USA Inc. (http://www.zend.com)
- * @license   http://framework.zend.com/license/new-bsd New BSD License
+ * @see       https://github.com/zendframework/zend-db for the canonical source repository
+ * @copyright Copyright (c) 2005-2019 Zend Technologies USA Inc. (https://www.zend.com)
+ * @license   https://github.com/zendframework/zend-db/blob/master/LICENSE.md New BSD License
  */
 
+declare(strict_types=1);
+
 namespace Zend\Db\Sql\Predicate;
 
 class NotIn extends In
 {
+    /** @var string */
     protected $specification = '%s NOT IN %s';
 }
diff --git a/src/Sql/Predicate/NotLike.php b/src/Sql/Predicate/NotLike.php
index 18d627c551..ad45554990 100644
--- a/src/Sql/Predicate/NotLike.php
+++ b/src/Sql/Predicate/NotLike.php
@@ -1,15 +1,16 @@
 <?php
 /**
- * Zend Framework (http://framework.zend.com/)
- *
- * @link      http://github.com/zendframework/zf2 for the canonical source repository
- * @copyright Copyright (c) 2005-2016 Zend Technologies USA Inc. (http://www.zend.com)
- * @license   http://framework.zend.com/license/new-bsd New BSD License
+ * @see       https://github.com/zendframework/zend-db for the canonical source repository
+ * @copyright Copyright (c) 2005-2019 Zend Technologies USA Inc. (https://www.zend.com)
+ * @license   https://github.com/zendframework/zend-db/blob/master/LICENSE.md New BSD License
  */
 
+declare(strict_types=1);
+
 namespace Zend\Db\Sql\Predicate;
 
 class NotLike extends Like
 {
+    /** @var string */
     protected $specification = '%1$s NOT LIKE %2$s';
 }
diff --git a/src/Sql/Predicate/Operator.php b/src/Sql/Predicate/Operator.php
index 5326d605ad..91e106f28a 100644
--- a/src/Sql/Predicate/Operator.php
+++ b/src/Sql/Predicate/Operator.php
@@ -1,68 +1,58 @@
 <?php
 /**
- * Zend Framework (http://framework.zend.com/)
- *
- * @link      http://github.com/zendframework/zf2 for the canonical source repository
- * @copyright Copyright (c) 2005-2016 Zend Technologies USA Inc. (http://www.zend.com)
- * @license   http://framework.zend.com/license/new-bsd New BSD License
+ * @see       https://github.com/zendframework/zend-db for the canonical source repository
+ * @copyright Copyright (c) 2005-2019 Zend Technologies USA Inc. (https://www.zend.com)
+ * @license   https://github.com/zendframework/zend-db/blob/master/LICENSE.md New BSD License
  */
 
+declare(strict_types=1);
+
 namespace Zend\Db\Sql\Predicate;
 
-use Zend\Db\Sql\Exception;
 use Zend\Db\Sql\AbstractExpression;
+use Zend\Db\Sql\Exception;
+use function in_array;
+use function is_array;
+use function sprintf;
 
 class Operator extends AbstractExpression implements PredicateInterface
 {
-    const OPERATOR_EQUAL_TO                  = '=';
-    const OP_EQ                              = '=';
+    public const OPERATOR_EQUAL_TO                  = '=';
+    public const OP_EQ                              = '=';
 
-    const OPERATOR_NOT_EQUAL_TO              = '!=';
-    const OP_NE                              = '!=';
+    public const OPERATOR_NOT_EQUAL_TO              = '!=';
+    public const OP_NE                              = '!=';
 
-    const OPERATOR_LESS_THAN                 = '<';
-    const OP_LT                              = '<';
+    public const OPERATOR_LESS_THAN                 = '<';
+    public const OP_LT                              = '<';
 
-    const OPERATOR_LESS_THAN_OR_EQUAL_TO     = '<=';
-    const OP_LTE                             = '<=';
+    public const OPERATOR_LESS_THAN_OR_EQUAL_TO     = '<=';
+    public const OP_LTE                             = '<=';
 
-    const OPERATOR_GREATER_THAN              = '>';
-    const OP_GT                              = '>';
+    public const OPERATOR_GREATER_THAN              = '>';
+    public const OP_GT                              = '>';
 
-    const OPERATOR_GREATER_THAN_OR_EQUAL_TO  = '>=';
-    const OP_GTE                             = '>=';
+    public const OPERATOR_GREATER_THAN_OR_EQUAL_TO  = '>=';
+    public const OP_GTE                             = '>=';
 
-    /**
-     * {@inheritDoc}
-     */
     protected $allowedTypes  = [
         self::TYPE_IDENTIFIER,
         self::TYPE_VALUE,
     ];
 
-    /**
-     * @var int|float|bool|string
-     */
+    /** @var int|float|bool|string */
     protected $left;
 
-    /**
-     * @var int|float|bool|string
-     */
+    /** @var int|float|bool|string */
     protected $right;
 
-    /**
-     * @var string
-     */
+    /** @var string */
     protected $leftType = self::TYPE_IDENTIFIER;
 
-    /**
-     * @var string
-     */
+    /** @var string */
     protected $rightType = self::TYPE_VALUE;
 
-    /**
-     * @var string
-     */
+    /** @var string */
     protected $operator = self::OPERATOR_EQUAL_TO;
 
     /**
@@ -76,10 +66,10 @@ class Operator extends AbstractExpression implements PredicateInterface
      */
     public function __construct(
         $left = null,
-        $operator = self::OPERATOR_EQUAL_TO,
+        string $operator = self::OPERATOR_EQUAL_TO,
         $right = null,
-        $leftType = self::TYPE_IDENTIFIER,
-        $rightType = self::TYPE_VALUE
+        string $leftType = self::TYPE_IDENTIFIER,
+        string $rightType = self::TYPE_VALUE
     ) {
         if ($left !== null) {
             $this->setLeft($left);
@@ -105,11 +95,10 @@ public function __construct(
     /**
      * Set left side of operator
      *
-     * @param  int|float|bool|string $left
-     *
-     * @return self Provides a fluent interface
+     * @param int|float|bool|string $left
+     * @return $this
      */
-    public function setLeft($left)
+    public function setLeft($left) : self
     {
         $this->left = $left;
 
@@ -123,7 +112,6 @@ public function setLeft($left)
 
     /**
      * Get left side of operator
-     *
      * @return int|float|bool|string
      */
     public function getLeft()
@@ -134,13 +122,11 @@ public function getLeft()
     /**
      * Set parameter type for left side of operator
      *
-     * @param  string $type TYPE_IDENTIFIER or TYPE_VALUE {@see allowedTypes}
-     *
-     * @return self Provides a fluent interface
-     *
+     * @param string $type TYPE_IDENTIFIER or TYPE_VALUE {@see allowedTypes}
+     * @return $this
      * @throws Exception\InvalidArgumentException
      */
-    public function setLeftType($type)
+    public function setLeftType($type) : self
     {
         if (! in_array($type, $this->allowedTypes)) {
             throw new Exception\InvalidArgumentException(sprintf(
@@ -156,35 +142,19 @@ public function setLeftType($type)
         return $this;
     }
 
-    /**
-     * Get parameter type on left side of operator
-     *
-     * @return string
-     */
-    public function getLeftType()
+    public function getLeftType() : string
     {
         return $this->leftType;
     }
 
-    /**
-     * Set operator string
-     *
-     * @param  string $operator
-     * @return self Provides a fluent interface
-     */
-    public function setOperator($operator)
+    public function setOperator(string $operator) : self
     {
         $this->operator = $operator;
 
         return $this;
     }
 
-    /**
-     * Get operator string
-     *
-     * @return string
-     */
-    public function getOperator()
+    public function getOperator() : string
     {
         return $this->operator;
     }
@@ -192,11 +162,10 @@ public function getOperator()
     /**
      * Set right side of operator
      *
-     * @param  int|float|bool|string $right
-     *
-     * @return self Provides a fluent interface
+     * @param int|float|bool|string $right
+     * @return $this
      */
-    public function setRight($right)
+    public function setRight($right) : self
     {
         $this->right = $right;
 
@@ -210,7 +179,6 @@ public function setRight($right)
 
     /**
      * Get right side of operator
-     *
      * @return int|float|bool|string
      */
     public function getRight()
@@ -221,11 +189,12 @@ public function getRight()
     /**
      * Set parameter type for right side of operator
      *
-     * @param  string $type TYPE_IDENTIFIER or TYPE_VALUE {@see allowedTypes}
-     * @return self Provides a fluent interface
+     * @param string $type TYPE_IDENTIFIER or TYPE_VALUE {@see allowedTypes}
+     * @return $this
+     *
      * @throws Exception\InvalidArgumentException
      */
-    public function setRightType($type)
+    public function setRightType(string $type) : self
     {
         if (! in_array($type, $this->allowedTypes)) {
             throw new Exception\InvalidArgumentException(sprintf(
@@ -241,22 +210,12 @@ public function setRightType($type)
         return $this;
     }
 
-    /**
-     * Get parameter type on right side of operator
-     *
-     * @return string
-     */
-    public function getRightType()
+    public function getRightType() : string
     {
         return $this->rightType;
     }
 
-    /**
-     * Get predicate parts for where statement
-     *
-     * @return array
-     */
-    public function getExpressionData()
+    public function getExpressionData() : array
     {
         list($values[], $types[]) = $this->normalizeArgument($this->left, $this->leftType);
         list($values[], $types[]) = $this->normalizeArgument($this->right, $this->rightType);
@@ -264,7 +223,7 @@ public function getExpressionData()
         return [[
             '%s ' . $this->operator . ' %s',
             $values,
-            $types
+            $types,
         ]];
     }
 }
diff --git a/src/Sql/Predicate/Predicate.php b/src/Sql/Predicate/Predicate.php
index a7d901d7bf..ab61695d63 100644
--- a/src/Sql/Predicate/Predicate.php
+++ b/src/Sql/Predicate/Predicate.php
@@ -1,15 +1,19 @@
 <?php
 /**
- * Zend Framework (http://framework.zend.com/)
- *
- * @link      http://github.com/zendframework/zf2 for the canonical source repository
- * @copyright Copyright (c) 2005-2016 Zend Technologies USA Inc. (http://www.zend.com)
- * @license   http://framework.zend.com/license/new-bsd New BSD License
+ * @see       https://github.com/zendframework/zend-db for the canonical source repository
+ * @copyright Copyright (c) 2005-2019 Zend Technologies USA Inc. (https://www.zend.com)
+ * @license   https://github.com/zendframework/zend-db/blob/master/LICENSE.md New BSD License
  */
 
+declare(strict_types=1);
+
 namespace Zend\Db\Sql\Predicate;
 
 use Zend\Db\Sql\Exception\RuntimeException;
+use Zend\Db\Sql\Select;
+use function func_get_arg;
+use function func_num_args;
+use function strtolower;
 
 /**
  * @property Predicate $and
@@ -21,47 +25,34 @@
  */
 class Predicate extends PredicateSet
 {
-    protected $unnest = null;
-    protected $nextPredicateCombineOperator = null;
+    protected $unnest;
+    protected $nextPredicateCombineOperator;
 
-    /**
-     * Begin nesting predicates
-     *
-     * @return Predicate
-     */
-    public function nest()
+    public function nest() : Predicate
     {
-        $predicateSet = new Predicate();
+        $predicateSet = new self();
         $predicateSet->setUnnest($this);
-        $this->addPredicate($predicateSet, ($this->nextPredicateCombineOperator) ?: $this->defaultCombination);
+
+        $this->addPredicate($predicateSet, $this->nextPredicateCombineOperator ?? $this->defaultCombination);
         $this->nextPredicateCombineOperator = null;
+
         return $predicateSet;
     }
 
-    /**
-     * Indicate what predicate will be unnested
-     *
-     * @param  Predicate $predicate
-     * @return void
-     */
-    public function setUnnest(Predicate $predicate)
+    public function setUnnest(Predicate $predicate) : void
     {
         $this->unnest = $predicate;
     }
 
-    /**
-     * Indicate end of nested predicate
-     *
-     * @return Predicate
-     * @throws RuntimeException
-     */
-    public function unnest()
+    public function unnest() : Predicate
     {
         if ($this->unnest === null) {
             throw new RuntimeException('Not nested');
         }
+
         $unnest       = $this->unnest;
         $this->unnest = null;
+
         return $unnest;
     }
 
@@ -70,18 +61,23 @@ public function unnest()
      *
      * Utilizes Operator predicate
      *
-     * @param  int|float|bool|string $left
-     * @param  int|float|bool|string $right
-     * @param  string $leftType TYPE_IDENTIFIER or TYPE_VALUE by default TYPE_IDENTIFIER {@see allowedTypes}
-     * @param  string $rightType TYPE_IDENTIFIER or TYPE_VALUE by default TYPE_VALUE {@see allowedTypes}
-     * @return self Provides a fluent interface
+     * @param int|float|bool|string $left
+     * @param int|float|bool|string $right
+     * @param string $leftType TYPE_IDENTIFIER or TYPE_VALUE by default TYPE_IDENTIFIER {@see allowedTypes}
+     * @param string $rightType TYPE_IDENTIFIER or TYPE_VALUE by default TYPE_VALUE {@see allowedTypes}
+     * @return $this
      */
-    public function equalTo($left, $right, $leftType = self::TYPE_IDENTIFIER, $rightType = self::TYPE_VALUE)
-    {
+    public function equalTo(
+        $left,
+        $right,
+        string  $leftType = self::TYPE_IDENTIFIER,
+        ?string $rightType = self::TYPE_VALUE
+    ) : self {
         $this->addPredicate(
             new Operator($left, Operator::OPERATOR_EQUAL_TO, $right, $leftType, $rightType),
-            ($this->nextPredicateCombineOperator) ?: $this->defaultCombination
+            $this->nextPredicateCombineOperator ?? $this->defaultCombination
         );
+
         $this->nextPredicateCombineOperator = null;
 
         return $this;
@@ -92,18 +88,23 @@ public function equalTo($left, $right, $leftType = self::TYPE_IDENTIFIER, $right
      *
      * Utilizes Operator predicate
      *
-     * @param  int|float|bool|string $left
-     * @param  int|float|bool|string $right
-     * @param  string $leftType TYPE_IDENTIFIER or TYPE_VALUE by default TYPE_IDENTIFIER {@see allowedTypes}
-     * @param  string $rightType TYPE_IDENTIFIER or TYPE_VALUE by default TYPE_VALUE {@see allowedTypes}
-     * @return self Provides a fluent interface
+     * @param int|float|bool|string $left
+     * @param int|float|bool|string $right
+     * @param string $leftType TYPE_IDENTIFIER or TYPE_VALUE by default TYPE_IDENTIFIER {@see allowedTypes}
+     * @param string $rightType TYPE_IDENTIFIER or TYPE_VALUE by default TYPE_VALUE {@see allowedTypes}
+     * @return $this
      */
-    public function notEqualTo($left, $right, $leftType = self::TYPE_IDENTIFIER, $rightType = self::TYPE_VALUE)
-    {
+    public function notEqualTo(
+        $left,
+        $right,
+        string $leftType = self::TYPE_IDENTIFIER,
+        string $rightType = self::TYPE_VALUE
+    ) : self {
         $this->addPredicate(
             new Operator($left, Operator::OPERATOR_NOT_EQUAL_TO, $right, $leftType, $rightType),
-            ($this->nextPredicateCombineOperator) ?: $this->defaultCombination
+            $this->nextPredicateCombineOperator ?? $this->defaultCombination
         );
+
         $this->nextPredicateCombineOperator = null;
 
         return $this;
@@ -114,18 +115,23 @@ public function notEqualTo($left, $right, $leftType = self::TYPE_IDENTIFIER, $ri
      *
      * Utilizes Operator predicate
      *
-     * @param  int|float|bool|string $left
-     * @param  int|float|bool|string $right
-     * @param  string $leftType TYPE_IDENTIFIER or TYPE_VALUE by default TYPE_IDENTIFIER {@see allowedTypes}
-     * @param  string $rightType TYPE_IDENTIFIER or TYPE_VALUE by default TYPE_VALUE {@see allowedTypes}
-     * @return self Provides a fluent interface
+     * @param int|float|bool|string $left
+     * @param int|float|bool|string $right
+     * @param string $leftType TYPE_IDENTIFIER or TYPE_VALUE by default TYPE_IDENTIFIER {@see allowedTypes}
+     * @param string $rightType TYPE_IDENTIFIER or TYPE_VALUE by default TYPE_VALUE {@see allowedTypes}
+     * @return $this
      */
-    public function lessThan($left, $right, $leftType = self::TYPE_IDENTIFIER, $rightType = self::TYPE_VALUE)
-    {
+    public function lessThan(
+        $left,
+        $right,
+        string $leftType = self::TYPE_IDENTIFIER,
+        string $rightType = self::TYPE_VALUE
+    ) : self {
         $this->addPredicate(
             new Operator($left, Operator::OPERATOR_LESS_THAN, $right, $leftType, $rightType),
-            ($this->nextPredicateCombineOperator) ?: $this->defaultCombination
+            $this->nextPredicateCombineOperator ?? $this->defaultCombination
         );
+
         $this->nextPredicateCombineOperator = null;
 
         return $this;
@@ -136,18 +142,23 @@ public function lessThan($left, $right, $leftType = self::TYPE_IDENTIFIER, $righ
      *
      * Utilizes Operator predicate
      *
-     * @param  int|float|bool|string $left
-     * @param  int|float|bool|string $right
-     * @param  string $leftType TYPE_IDENTIFIER or TYPE_VALUE by default TYPE_IDENTIFIER {@see allowedTypes}
-     * @param  string $rightType TYPE_IDENTIFIER or TYPE_VALUE by default TYPE_VALUE {@see allowedTypes}
-     * @return self Provides a fluent interface
+     * @param int|float|bool|string $left
+     * @param int|float|bool|string $right
+     * @param string $leftType TYPE_IDENTIFIER or TYPE_VALUE by default TYPE_IDENTIFIER {@see allowedTypes}
+     * @param string $rightType TYPE_IDENTIFIER or TYPE_VALUE by default TYPE_VALUE {@see allowedTypes}
+     * @return $this
      */
-    public function greaterThan($left, $right, $leftType = self::TYPE_IDENTIFIER, $rightType = self::TYPE_VALUE)
-    {
+    public function greaterThan(
+        $left,
+        $right,
+        string $leftType = self::TYPE_IDENTIFIER,
+        string $rightType = self::TYPE_VALUE
+    ) : self {
         $this->addPredicate(
             new Operator($left, Operator::OPERATOR_GREATER_THAN, $right, $leftType, $rightType),
-            ($this->nextPredicateCombineOperator) ?: $this->defaultCombination
+            $this->nextPredicateCombineOperator ?? $this->defaultCombination
         );
+
         $this->nextPredicateCombineOperator = null;
 
         return $this;
@@ -158,18 +169,23 @@ public function greaterThan($left, $right, $leftType = self::TYPE_IDENTIFIER, $r
      *
      * Utilizes Operator predicate
      *
-     * @param  int|float|bool|string $left
-     * @param  int|float|bool|string $right
-     * @param  string $leftType TYPE_IDENTIFIER or TYPE_VALUE by default TYPE_IDENTIFIER {@see allowedTypes}
-     * @param  string $rightType TYPE_IDENTIFIER or TYPE_VALUE by default TYPE_VALUE {@see allowedTypes}
-     * @return self Provides a fluent interface
+     * @param int|float|bool|string $left
+     * @param int|float|bool|string $right
+     * @param string $leftType TYPE_IDENTIFIER or TYPE_VALUE by default TYPE_IDENTIFIER {@see allowedTypes}
+     * @param string $rightType TYPE_IDENTIFIER or TYPE_VALUE by default TYPE_VALUE {@see allowedTypes}
+     * @return $this
      */
-    public function lessThanOrEqualTo($left, $right, $leftType = self::TYPE_IDENTIFIER, $rightType = self::TYPE_VALUE)
-    {
+    public function lessThanOrEqualTo(
+        $left,
+        $right,
+        string $leftType = self::TYPE_IDENTIFIER,
+        string $rightType = self::TYPE_VALUE
+    ) : self {
         $this->addPredicate(
             new Operator($left, Operator::OPERATOR_LESS_THAN_OR_EQUAL_TO, $right, $leftType, $rightType),
-            ($this->nextPredicateCombineOperator) ?: $this->defaultCombination
+            $this->nextPredicateCombineOperator ?? $this->defaultCombination
         );
+
         $this->nextPredicateCombineOperator = null;
 
         return $this;
@@ -180,22 +196,23 @@ public function lessThanOrEqualTo($left, $right, $leftType = self::TYPE_IDENTIFI
      *
      * Utilizes Operator predicate
      *
-     * @param  int|float|bool|string $left
-     * @param  int|float|bool|string $right
-     * @param  string $leftType TYPE_IDENTIFIER or TYPE_VALUE by default TYPE_IDENTIFIER {@see allowedTypes}
-     * @param  string $rightType TYPE_IDENTIFIER or TYPE_VALUE by default TYPE_VALUE {@see allowedTypes}
-     * @return self Provides a fluent interface
+     * @param int|float|bool|string $left
+     * @param int|float|bool|string $right
+     * @param string $leftType TYPE_IDENTIFIER or TYPE_VALUE by default TYPE_IDENTIFIER {@see allowedTypes}
+     * @param string $rightType TYPE_IDENTIFIER or TYPE_VALUE by default TYPE_VALUE {@see allowedTypes}
+     * @return $this
      */
     public function greaterThanOrEqualTo(
         $left,
         $right,
-        $leftType = self::TYPE_IDENTIFIER,
-        $rightType = self::TYPE_VALUE
-    ) {
+        string $leftType = self::TYPE_IDENTIFIER,
+        string $rightType = self::TYPE_VALUE
+    ) : self {
         $this->addPredicate(
             new Operator($left, Operator::OPERATOR_GREATER_THAN_OR_EQUAL_TO, $right, $leftType, $rightType),
-            ($this->nextPredicateCombineOperator) ?: $this->defaultCombination
+            $this->nextPredicateCombineOperator ?? $this->defaultCombination
         );
+
         $this->nextPredicateCombineOperator = null;
 
         return $this;
@@ -206,16 +223,17 @@ public function greaterThanOrEqualTo(
      *
      * Utilizes Like predicate
      *
-     * @param  string|Expression $identifier
-     * @param  string $like
-     * @return self Provides a fluent interface
+     * @param string|Expression $identifier
+     * @param string            $like
+     * @return $this
      */
-    public function like($identifier, $like)
+    public function like($identifier, string $like) : self
     {
         $this->addPredicate(
             new Like($identifier, $like),
-            ($this->nextPredicateCombineOperator) ?: $this->defaultCombination
+            $this->nextPredicateCombineOperator ?? $this->defaultCombination
         );
+
         $this->nextPredicateCombineOperator = null;
 
         return $this;
@@ -225,17 +243,19 @@ public function like($identifier, $like)
      *
      * Utilizes In predicate
      *
-     * @param  string|Expression $identifier
-     * @param  string $notLike
-     * @return self Provides a fluent interface
+     * @param string|Expression $identifier
+     * @param string            $notLike
+     * @return $this
      */
-    public function notLike($identifier, $notLike)
+    public function notLike($identifier, string $notLike) : self
     {
         $this->addPredicate(
             new NotLike($identifier, $notLike),
-            ($this->nextPredicateCombineOperator) ? : $this->defaultCombination
+            $this->nextPredicateCombineOperator ?? $this->defaultCombination
         );
+
         $this->nextPredicateCombineOperator = null;
+
         return $this;
     }
 
@@ -244,14 +264,15 @@ public function notLike($identifier, $notLike)
      *
      * @param $expression
      * @param $parameters
-     * @return self Provides a fluent interface
+     * @return $this
      */
-    public function expression($expression, $parameters = null)
+    public function expression($expression, $parameters = null) : self
     {
         $this->addPredicate(
             new Expression($expression, $parameters),
-            ($this->nextPredicateCombineOperator) ?: $this->defaultCombination
+            $this->nextPredicateCombineOperator ?? $this->defaultCombination
         );
+
         $this->nextPredicateCombineOperator = null;
 
         return $this;
@@ -262,10 +283,10 @@ public function expression($expression, $parameters = null)
      *
      * Literal predicate, for parameters, use expression()
      *
-     * @param  string $literal
-     * @return self Provides a fluent interface
+     * @param string $literal
+     * @return $this
      */
-    public function literal($literal)
+    public function literal(string $literal) : self
     {
         // process deprecated parameters from previous literal($literal, $parameters = null) signature
         if (func_num_args() >= 2) {
@@ -280,8 +301,9 @@ public function literal($literal)
 
         $this->addPredicate(
             $predicate,
-            ($this->nextPredicateCombineOperator) ?: $this->defaultCombination
+            $this->nextPredicateCombineOperator ?? $this->defaultCombination
         );
+
         $this->nextPredicateCombineOperator = null;
 
         return $this;
@@ -292,15 +314,16 @@ public function literal($literal)
      *
      * Utilizes IsNull predicate
      *
-     * @param  string|Expression $identifier
-     * @return self Provides a fluent interface
+     * @param string|Expression $identifier
+     * @return $this
      */
-    public function isNull($identifier)
+    public function isNull($identifier) : self
     {
         $this->addPredicate(
             new IsNull($identifier),
-            ($this->nextPredicateCombineOperator) ?: $this->defaultCombination
+            $this->nextPredicateCombineOperator ?? $this->defaultCombination
         );
+
         $this->nextPredicateCombineOperator = null;
 
         return $this;
@@ -311,15 +334,16 @@ public function isNull($identifier)
      *
      * Utilizes IsNotNull predicate
      *
-     * @param  string|Expression $identifier
-     * @return self Provides a fluent interface
+     * @param string|Expression $identifier
+     * @return $this
      */
-    public function isNotNull($identifier)
+    public function isNotNull($identifier) : self
     {
         $this->addPredicate(
             new IsNotNull($identifier),
-            ($this->nextPredicateCombineOperator) ?: $this->defaultCombination
+            $this->nextPredicateCombineOperator ?? $this->defaultCombination
         );
+
         $this->nextPredicateCombineOperator = null;
 
         return $this;
@@ -330,16 +354,17 @@ public function isNotNull($identifier)
      *
      * Utilizes In predicate
      *
-     * @param  string|Expression $identifier
-     * @param  array|\Zend\Db\Sql\Select $valueSet
-     * @return self Provides a fluent interface
+     * @param string|Expression $identifier
+     * @param array|Select|null $valueSet
+     * @return s$this
      */
-    public function in($identifier, $valueSet = null)
+    public function in($identifier, $valueSet = null) : self
     {
         $this->addPredicate(
             new In($identifier, $valueSet),
-            ($this->nextPredicateCombineOperator) ?: $this->defaultCombination
+            $this->nextPredicateCombineOperator ?? $this->defaultCombination
         );
+
         $this->nextPredicateCombineOperator = null;
 
         return $this;
@@ -350,15 +375,15 @@ public function in($identifier, $valueSet = null)
      *
      * Utilizes NotIn predicate
      *
-     * @param  string|Expression $identifier
-     * @param  array|\Zend\Db\Sql\Select $valueSet
-     * @return self Provides a fluent interface
+     * @param string|Expression $identifier
+     * @param array|Select|null $valueSet
+     * @return $this
      */
-    public function notIn($identifier, $valueSet = null)
+    public function notIn($identifier, $valueSet = null) : self
     {
         $this->addPredicate(
             new NotIn($identifier, $valueSet),
-            ($this->nextPredicateCombineOperator) ?: $this->defaultCombination
+            $this->nextPredicateCombineOperator ?? $this->defaultCombination
         );
         $this->nextPredicateCombineOperator = null;
 
@@ -370,17 +395,18 @@ public function notIn($identifier, $valueSet = null)
      *
      * Utilizes Between predicate
      *
-     * @param  string|Expression $identifier
-     * @param  int|float|string $minValue
-     * @param  int|float|string $maxValue
-     * @return self Provides a fluent interface
+     * @param string|Expression $identifier
+     * @param int|float|string  $minValue
+     * @param int|float|string  $maxValue
+     * @return $this
      */
-    public function between($identifier, $minValue, $maxValue)
+    public function between($identifier, $minValue, $maxValue) : self
     {
         $this->addPredicate(
             new Between($identifier, $minValue, $maxValue),
-            ($this->nextPredicateCombineOperator) ?: $this->defaultCombination
+            $this->nextPredicateCombineOperator ?? $this->defaultCombination
         );
+
         $this->nextPredicateCombineOperator = null;
 
         return $this;
@@ -391,17 +417,18 @@ public function between($identifier, $minValue, $maxValue)
      *
      * Utilizes NotBetween predicate
      *
-     * @param  string|Expression $identifier
-     * @param  int|float|string $minValue
-     * @param  int|float|string $maxValue
-     * @return self Provides a fluent interface
+     * @param string|Expression $identifier
+     * @param int|float|string  $minValue
+     * @param int|float|string  $maxValue
+     * @return $this
      */
-    public function notBetween($identifier, $minValue, $maxValue)
+    public function notBetween($identifier, $minValue, $maxValue) : self
     {
         $this->addPredicate(
             new NotBetween($identifier, $minValue, $maxValue),
-            ($this->nextPredicateCombineOperator) ?: $this->defaultCombination
+            $this->nextPredicateCombineOperator ?? $this->defaultCombination
         );
+
         $this->nextPredicateCombineOperator = null;
 
         return $this;
@@ -414,15 +441,16 @@ public function notBetween($identifier, $minValue, $maxValue)
      * AND / OR combination operator, thus allowing generic predicates to be
      * used fluently within where chains as any other concrete predicate.
      *
-     * @param  PredicateInterface $predicate
-     * @return self Provides a fluent interface
+     * @param PredicateInterface $predicate
+     * @return $this
      */
-    public function predicate(PredicateInterface $predicate)
+    public function predicate(PredicateInterface $predicate) : self
     {
         $this->addPredicate(
             $predicate,
-            $this->nextPredicateCombineOperator ?: $this->defaultCombination
+            $this->nextPredicateCombineOperator ?? $this->defaultCombination
         );
+
         $this->nextPredicateCombineOperator = null;
 
         return $this;
@@ -433,10 +461,10 @@ public function predicate(PredicateInterface $predicate)
      *
      * Overloads "or", "and", "nest", and "unnest"
      *
-     * @param  string $name
-     * @return self Provides a fluent interface
+     * @param string $name
+     * @return mixed
      */
-    public function __get($name)
+    public function __get(string $name)
     {
         switch (strtolower($name)) {
             case 'or':
@@ -450,6 +478,7 @@ public function __get($name)
             case 'unnest':
                 return $this->unnest();
         }
+
         return $this;
     }
 }
diff --git a/src/Sql/Predicate/PredicateInterface.php b/src/Sql/Predicate/PredicateInterface.php
index b8d6c84baf..47487e0c12 100644
--- a/src/Sql/Predicate/PredicateInterface.php
+++ b/src/Sql/Predicate/PredicateInterface.php
@@ -1,12 +1,12 @@
 <?php
 /**
- * Zend Framework (http://framework.zend.com/)
- *
- * @link      http://github.com/zendframework/zf2 for the canonical source repository
- * @copyright Copyright (c) 2005-2016 Zend Technologies USA Inc. (http://www.zend.com)
- * @license   http://framework.zend.com/license/new-bsd New BSD License
+ * @see       https://github.com/zendframework/zend-db for the canonical source repository
+ * @copyright Copyright (c) 2005-2019 Zend Technologies USA Inc. (https://www.zend.com)
+ * @license   https://github.com/zendframework/zend-db/blob/master/LICENSE.md New BSD License
  */
 
+declare(strict_types=1);
+
 namespace Zend\Db\Sql\Predicate;
 
 use Zend\Db\Sql\ExpressionInterface;
diff --git a/src/Sql/Predicate/PredicateSet.php b/src/Sql/Predicate/PredicateSet.php
index 9bf545dc75..a8c7e452f3 100644
--- a/src/Sql/Predicate/PredicateSet.php
+++ b/src/Sql/Predicate/PredicateSet.php
@@ -1,37 +1,40 @@
 <?php
 /**
- * Zend Framework (http://framework.zend.com/)
- *
- * @link      http://github.com/zendframework/zf2 for the canonical source repository
- * @copyright Copyright (c) 2005-2016 Zend Technologies USA Inc. (http://www.zend.com)
- * @license   http://framework.zend.com/license/new-bsd New BSD License
+ * @see       https://github.com/zendframework/zend-db for the canonical source repository
+ * @copyright Copyright (c) 2005-2019 Zend Technologies USA Inc. (https://www.zend.com)
+ * @license   https://github.com/zendframework/zend-db/blob/master/LICENSE.md New BSD License
  */
 
+declare(strict_types=1);
+
 namespace Zend\Db\Sql\Predicate;
 
 use Countable;
 use Zend\Db\Sql\Exception;
+use function array_merge;
+use function count;
+use function in_array;
+use function is_string;
+use function sprintf;
+use function strpos;
 
 class PredicateSet implements PredicateInterface, Countable
 {
-    const COMBINED_BY_AND = 'AND';
-    const OP_AND          = 'AND';
-
-    const COMBINED_BY_OR  = 'OR';
-    const OP_OR           = 'OR';
+    public const COMBINED_BY_AND = 'AND';
+    public const OP_AND          = 'AND';
+    public const COMBINED_BY_OR  = 'OR';
+    public const OP_OR           = 'OR';
 
+    /** @var string  */
     protected $defaultCombination = self::COMBINED_BY_AND;
+
+    /** @var PredicateInterface[] */
     protected $predicates         = [];
 
-    /**
-     * Constructor
-     *
-     * @param  null|array $predicates
-     * @param  string $defaultCombination
-     */
-    public function __construct(array $predicates = null, $defaultCombination = self::COMBINED_BY_AND)
+    public function __construct(?array $predicates = null, string $defaultCombination = self::COMBINED_BY_AND)
     {
         $this->defaultCombination = $defaultCombination;
+
         if ($predicates) {
             foreach ($predicates as $predicate) {
                 $this->addPredicate($predicate);
@@ -39,25 +42,20 @@ public function __construct(array $predicates = null, $defaultCombination = self
         }
     }
 
-    /**
-     * Add predicate to set
-     *
-     * @param  PredicateInterface $predicate
-     * @param  string $combination
-     * @return self Provides a fluent interface
-     */
-    public function addPredicate(PredicateInterface $predicate, $combination = null)
+    public function addPredicate(PredicateInterface $predicate, ?string $combination = null) : self
     {
         if ($combination === null || ! in_array($combination, [self::OP_AND, self::OP_OR])) {
             $combination = $this->defaultCombination;
         }
 
-        if ($combination == self::OP_OR) {
+        if ($combination === self::OP_OR) {
             $this->orPredicate($predicate);
+
             return $this;
         }
 
         $this->andPredicate($predicate);
+
         return $this;
     }
 
@@ -65,30 +63,38 @@ public function addPredicate(PredicateInterface $predicate, $combination = null)
      * Add predicates to set
      *
      * @param PredicateInterface|\Closure|string|array $predicates
-     * @param string $combination
-     * @return self Provides a fluent interface
+     * @param string                                   $combination
+     * @return $this
+     *
      * @throws Exception\InvalidArgumentException
      */
-    public function addPredicates($predicates, $combination = self::OP_AND)
+    public function addPredicates($predicates, string $combination = self::OP_AND) : self
     {
         if ($predicates === null) {
             throw new Exception\InvalidArgumentException('Predicate cannot be null');
         }
+
         if ($predicates instanceof PredicateInterface) {
             $this->addPredicate($predicates, $combination);
+
             return $this;
         }
+
         if ($predicates instanceof \Closure) {
             $predicates($this);
+
             return $this;
         }
+
         if (is_string($predicates)) {
             // String $predicate should be passed as an expression
             $predicates = (strpos($predicates, Expression::PLACEHOLDER) !== false)
                 ? new Expression($predicates) : new Literal($predicates);
             $this->addPredicate($predicates, $combination);
+
             return $this;
         }
+
         if (is_array($predicates)) {
             foreach ($predicates as $pkey => $pvalue) {
                 // loop through predicates
@@ -120,65 +126,48 @@ public function addPredicates($predicates, $combination = self::OP_AND)
                     $predicates = (strpos($pvalue, Expression::PLACEHOLDER) !== false)
                         ? new Expression($pvalue) : new Literal($pvalue);
                 }
+
                 $this->addPredicate($predicates, $combination);
             }
         }
+
         return $this;
     }
 
-    /**
-     * Return the predicates
-     *
-     * @return PredicateInterface[]
-     */
-    public function getPredicates()
+    public function getPredicates() : array
     {
         return $this->predicates;
     }
 
-    /**
-     * Add predicate using OR operator
-     *
-     * @param  PredicateInterface $predicate
-     * @return self Provides a fluent interface
-     */
-    public function orPredicate(PredicateInterface $predicate)
+    public function orPredicate(PredicateInterface $predicate) : self
     {
         $this->predicates[] = [self::OP_OR, $predicate];
+
         return $this;
     }
 
-    /**
-     * Add predicate using AND operator
-     *
-     * @param  PredicateInterface $predicate
-     * @return self Provides a fluent interface
-     */
-    public function andPredicate(PredicateInterface $predicate)
+    public function andPredicate(PredicateInterface $predicate) : self
     {
         $this->predicates[] = [self::OP_AND, $predicate];
+
         return $this;
     }
 
-    /**
-     * Get predicate parts for where statement
-     *
-     * @return array
-     */
-    public function getExpressionData()
+    public function getExpressionData() : array
     {
         $parts = [];
+
         for ($i = 0, $count = count($this->predicates); $i < $count; $i++) {
             /** @var $predicate PredicateInterface */
             $predicate = $this->predicates[$i][1];
 
-            if ($predicate instanceof PredicateSet) {
+            if ($predicate instanceof self) {
                 $parts[] = '(';
             }
 
             $parts = array_merge($parts, $predicate->getExpressionData());
 
-            if ($predicate instanceof PredicateSet) {
+            if ($predicate instanceof self) {
                 $parts[] = ')';
             }
 
@@ -186,15 +175,11 @@ public function getExpressionData()
                 $parts[] = sprintf(' %s ', $this->predicates[$i + 1][0]);
             }
         }
+
         return $parts;
     }
 
-    /**
-     * Get count of attached predicates
-     *
-     * @return int
-     */
-    public function count()
+    public function count() : int
     {
         return count($this->predicates);
     }
diff --git a/src/Sql/PreparableSqlInterface.php b/src/Sql/PreparableSqlInterface.php
index f937e07b7b..d93464a3d3 100644
--- a/src/Sql/PreparableSqlInterface.php
+++ b/src/Sql/PreparableSqlInterface.php
@@ -1,12 +1,12 @@
 <?php
 /**
- * Zend Framework (http://framework.zend.com/)
- *
- * @link      http://github.com/zendframework/zf2 for the canonical source repository
- * @copyright Copyright (c) 2005-2016 Zend Technologies USA Inc. (http://www.zend.com)
- * @license   http://framework.zend.com/license/new-bsd New BSD License
+ * @see       https://github.com/zendframework/zend-db for the canonical source repository
+ * @copyright Copyright (c) 2005-2019 Zend Technologies USA Inc. (https://www.zend.com)
+ * @license   https://github.com/zendframework/zend-db/blob/master/LICENSE.md New BSD License
  */
 
+declare(strict_types=1);
+
 namespace Zend\Db\Sql;
 
 use Zend\Db\Adapter\AdapterInterface;
@@ -14,11 +14,5 @@
 
 interface PreparableSqlInterface
 {
-    /**
-     * @param AdapterInterface            $adapter
-     * @param StatementContainerInterface $statementContainer
-     *
-     * @return void
-     */
     public function prepareStatement(AdapterInterface $adapter, StatementContainerInterface $statementContainer);
 }
diff --git a/src/Sql/Select.php b/src/Sql/Select.php
index c0d360e766..8df7f4b59f 100644
--- a/src/Sql/Select.php
+++ b/src/Sql/Select.php
@@ -1,20 +1,36 @@
 <?php
 /**
- * Zend Framework (http://framework.zend.com/)
- *
- * @link      http://github.com/zendframework/zf2 for the canonical source repository
- * @copyright Copyright (c) 2005-2016 Zend Technologies USA Inc. (http://www.zend.com)
- * @license   http://framework.zend.com/license/new-bsd New BSD License
+ * @see       https://github.com/zendframework/zend-db for the canonical source repository
+ * @copyright Copyright (c) 2005-2019 Zend Technologies USA Inc. (https://www.zend.com)
+ * @license   https://github.com/zendframework/zend-db/blob/master/LICENSE.md New BSD License
  */
 
+declare(strict_types=1);
+
 namespace Zend\Db\Sql;
 
 use Zend\Db\Adapter\Driver\DriverInterface;
 use Zend\Db\Adapter\ParameterContainer;
 use Zend\Db\Adapter\Platform\PlatformInterface;
+use Zend\Db\Sql\Predicate\PredicateInterface;
+use Zend\Db\Sql\Predicate\PredicateSet;
+use function compact;
+use function count;
+use function current;
+use function is_array;
+use function is_scalar;
+use function is_string;
+use function key;
+use function method_exists;
+use function preg_split;
+use function strcasecmp;
+use function stripos;
+use function strpos;
+use function strtolower;
+use function strtoupper;
+use function trim;
 
 /**
- *
  * @property Where $where
  * @property Having $having
  */
@@ -24,47 +40,47 @@ class Select extends AbstractPreparableSql
      * Constant
      * @const
      */
-    const SELECT = 'select';
-    const QUANTIFIER = 'quantifier';
-    const COLUMNS = 'columns';
-    const TABLE = 'table';
-    const JOINS = 'joins';
-    const WHERE = 'where';
-    const GROUP = 'group';
-    const HAVING = 'having';
-    const ORDER = 'order';
-    const LIMIT = 'limit';
-    const OFFSET = 'offset';
-    const QUANTIFIER_DISTINCT = 'DISTINCT';
-    const QUANTIFIER_ALL = 'ALL';
-    const JOIN_INNER = Join::JOIN_INNER;
-    const JOIN_OUTER = Join::JOIN_OUTER;
-    const JOIN_LEFT = Join::JOIN_LEFT;
-    const JOIN_RIGHT = Join::JOIN_RIGHT;
-    const JOIN_RIGHT_OUTER = Join::JOIN_RIGHT_OUTER;
-    const JOIN_LEFT_OUTER  = Join::JOIN_LEFT_OUTER;
-    const SQL_STAR = '*';
-    const ORDER_ASCENDING = 'ASC';
-    const ORDER_DESCENDING = 'DESC';
-    const COMBINE = 'combine';
-    const COMBINE_UNION = 'union';
-    const COMBINE_EXCEPT = 'except';
-    const COMBINE_INTERSECT = 'intersect';
+    public const SELECT = 'select';
+    public const QUANTIFIER = 'quantifier';
+    public const COLUMNS = 'columns';
+    public const TABLE = 'table';
+    public const JOINS = 'joins';
+    public const WHERE = 'where';
+    public const GROUP = 'group';
+    public const HAVING = 'having';
+    public const ORDER = 'order';
+    public const LIMIT = 'limit';
+    public const OFFSET = 'offset';
+    public const QUANTIFIER_DISTINCT = 'DISTINCT';
+    public const QUANTIFIER_ALL = 'ALL';
+    public const JOIN_INNER = Join::JOIN_INNER;
+    public const JOIN_OUTER = Join::JOIN_OUTER;
+    public const JOIN_LEFT = Join::JOIN_LEFT;
+    public const JOIN_RIGHT = Join::JOIN_RIGHT;
+    public const JOIN_RIGHT_OUTER = Join::JOIN_RIGHT_OUTER;
+    public const JOIN_LEFT_OUTER  = Join::JOIN_LEFT_OUTER;
+    public const SQL_STAR = '*';
+    public const ORDER_ASCENDING = 'ASC';
+    public const ORDER_DESCENDING = 'DESC';
+    public const COMBINE = 'combine';
+    public const COMBINE_UNION = 'union';
+    public const COMBINE_EXCEPT = 'except';
+    public const COMBINE_INTERSECT = 'intersect';
+
+    private const MODIFIER = 'modifier';
     /**#@-*/
 
     /**
      * @deprecated use JOIN_LEFT_OUTER instead
      */
-    const JOIN_OUTER_LEFT  = 'outer left';
+    public const JOIN_OUTER_LEFT  = 'outer left';
 
     /**
      * @deprecated use JOIN_LEFT_OUTER instead
      */
-    const JOIN_OUTER_RIGHT = 'outer right';
+    public const JOIN_OUTER_RIGHT = 'outer right';
 
-    /**
-     * @var array Specifications
-     */
+    /** @var array Specifications */
     protected $specifications = [
         'statementStart' => '%1$s',
         self::SELECT => [
@@ -84,19 +100,19 @@ class Select extends AbstractPreparableSql
         self::JOINS  => [
             '%1$s' => [
                 [3 => '%1$s JOIN %2$s ON %3$s', 'combinedby' => ' ']
-            ]
+            ],
         ],
         self::WHERE  => 'WHERE %1$s',
         self::GROUP  => [
             'GROUP BY %1$s' => [
                 [1 => '%1$s', 'combinedby' => ', ']
-            ]
+            ],
         ],
         self::HAVING => 'HAVING %1$s',
         self::ORDER  => [
             'ORDER BY %1$s' => [
                 [1 => '%1$s', 2 => '%1$s %2$s', 'combinedby' => ', ']
-            ]
+            ],
         ],
         self::LIMIT  => 'LIMIT %1$s',
         self::OFFSET => 'OFFSET %1$s',
@@ -104,75 +120,49 @@ class Select extends AbstractPreparableSql
         self::COMBINE => '%1$s ( %2$s )',
     ];
 
-    /**
-     * @var bool
-     */
+    /** @var bool */
     protected $tableReadOnly = false;
 
-    /**
-     * @var bool
-     */
+    /** @var bool */
     protected $prefixColumnsWithTable = true;
 
-    /**
-     * @var string|array|TableIdentifier
-     */
-    protected $table = null;
+    /** @var string|array|TableIdentifier */
+    protected $table;
 
-    /**
-     * @var null|string|Expression
-     */
-    protected $quantifier = null;
+    /** @var null|string|Expression */
+    protected $quantifier;
 
-    /**
-     * @var array
-     */
+    /** @var array */
     protected $columns = [self::SQL_STAR];
 
-    /**
-     * @var null|Join
-     */
-    protected $joins = null;
+    /** @var null|Join */
+    protected $joins;
 
-    /**
-     * @var Where
-     */
-    protected $where = null;
+    /** @var Where */
+    protected $where;
 
-    /**
-     * @var array
-     */
+    /** @var array */
     protected $order = [];
 
-    /**
-     * @var null|array
-     */
-    protected $group = null;
+    /** @var null|array */
+    protected $group;
 
-    /**
-     * @var null|string|array
-     */
-    protected $having = null;
+    /** @var null|string|array */
+    protected $having;
 
-    /**
-     * @var int|null
-     */
-    protected $limit = null;
+    /** @var int|null */
+    protected $limit;
 
-    /**
-     * @var int|null
-     */
-    protected $offset = null;
+    /** @var int|null */
+    protected $offset;
 
-    /**
-     * @var array
-     */
+    /** @var array */
     protected $combine = [];
 
     /**
      * Constructor
      *
-     * @param  null|string|array|TableIdentifier $table
+     * @param null|string|array|TableIdentifier $table
      */
     public function __construct($table = null)
     {
@@ -181,19 +171,19 @@ public function __construct($table = null)
             $this->tableReadOnly = true;
         }
 
-        $this->where = new Where;
-        $this->joins = new Join;
+        $this->where  = new Where;
+        $this->joins  = new Join;
         $this->having = new Having;
     }
 
     /**
      * Create from clause
      *
-     * @param  string|array|TableIdentifier $table
-     * @return self Provides a fluent interface
+     * @param string|array|TableIdentifier $table
+     * @return $this
      * @throws Exception\InvalidArgumentException
      */
-    public function from($table)
+    public function from($table) : self
     {
         if ($this->tableReadOnly) {
             throw new Exception\InvalidArgumentException(
@@ -219,10 +209,10 @@ public function from($table)
 
     /**
      * @param string|Expression $quantifier DISTINCT|ALL
-     * @return self Provides a fluent interface
+     * @return $this
      * @throws Exception\InvalidArgumentException
      */
-    public function quantifier($quantifier)
+    public function quantifier($quantifier) : self
     {
         if (! is_string($quantifier) && ! $quantifier instanceof ExpressionInterface) {
             throw new Exception\InvalidArgumentException(
@@ -231,6 +221,7 @@ public function quantifier($quantifier)
             );
         }
         $this->quantifier = $quantifier;
+
         return $this;
     }
 
@@ -248,28 +239,28 @@ public function quantifier($quantifier)
      *     key string will be use as alias,
      *     value can be string or Expression objects
      *
-     * @param  array $columns
-     * @param  bool  $prefixColumnsWithTable
-     * @return self Provides a fluent interface
+     * @param array $columns
+     * @param bool  $prefixColumnsWithTable
+     * @return $this
      */
-    public function columns(array $columns, $prefixColumnsWithTable = true)
+    public function columns(array $columns, bool $prefixColumnsWithTable = true) : self
     {
         $this->columns = $columns;
-        $this->prefixColumnsWithTable = (bool) $prefixColumnsWithTable;
+        $this->prefixColumnsWithTable = $prefixColumnsWithTable;
         return $this;
     }
 
     /**
      * Create join clause
      *
-     * @param  string|array|TableIdentifier $name
-     * @param  string|Predicate\Expression $on
-     * @param  string|array $columns
-     * @param  string $type one of the JOIN_* constants
-     * @return self Provides a fluent interface
+     * @param string|array|TableIdentifier $name
+     * @param string|Predicate\Expression  $on
+     * @param string|array                 $columns
+     * @param string                       $type one of the JOIN_* constants
+     * @return $this
      * @throws Exception\InvalidArgumentException
      */
-    public function join($name, $on, $columns = self::SQL_STAR, $type = self::JOIN_INNER)
+    public function join($name, $on, $columns = self::SQL_STAR, string $type = self::JOIN_INNER) : self
     {
         $this->joins->join($name, $on, $columns, $type);
 
@@ -279,12 +270,12 @@ public function join($name, $on, $columns = self::SQL_STAR, $type = self::JOIN_I
     /**
      * Create where clause
      *
-     * @param  Where|\Closure|string|array|Predicate\PredicateInterface $predicate
-     * @param  string $combination One of the OP_* constants from Predicate\PredicateSet
-     * @return self Provides a fluent interface
+     * @param Where|\Closure|string|array|PredicateInterface $predicate
+     * @param string $combination One of the OP_* constants from Predicate\PredicateSet
+     * @return $this
      * @throws Exception\InvalidArgumentException
      */
-    public function where($predicate, $combination = Predicate\PredicateSet::OP_AND)
+    public function where($predicate, string $combination = PredicateSet::OP_AND) : self
     {
         if ($predicate instanceof Where) {
             $this->where = $predicate;
@@ -296,9 +287,9 @@ public function where($predicate, $combination = Predicate\PredicateSet::OP_AND)
 
     /**
      * @param mixed $group
-     * @return self Provides a fluent interface
+     * @return $this
      */
-    public function group($group)
+    public function group($group) : self
     {
         if (is_array($group)) {
             foreach ($group as $o) {
@@ -313,11 +304,11 @@ public function group($group)
     /**
      * Create having clause
      *
-     * @param  Where|\Closure|string|array $predicate
-     * @param  string $combination One of the OP_* constants from Predicate\PredicateSet
-     * @return self Provides a fluent interface
+     * @param Where|\Closure|string|array $predicate
+     * @param string $combination One of the OP_* constants from Predicate\PredicateSet
+     * @return $this
      */
-    public function having($predicate, $combination = Predicate\PredicateSet::OP_AND)
+    public function having($predicate, string $combination = PredicateSet::OP_AND) : self
     {
         if ($predicate instanceof Having) {
             $this->having = $predicate;
@@ -329,9 +320,9 @@ public function having($predicate, $combination = Predicate\PredicateSet::OP_AND
 
     /**
      * @param string|array|Expression $order
-     * @return self Provides a fluent interface
+     * @return $this Provides a fluent interface
      */
-    public function order($order)
+    public function order($order) : self
     {
         if (is_string($order)) {
             if (strpos($order, ',') !== false) {
@@ -352,72 +343,30 @@ public function order($order)
         return $this;
     }
 
-    /**
-     * @param int $limit
-     * @return self Provides a fluent interface
-     * @throws Exception\InvalidArgumentException
-     */
-    public function limit($limit)
+    public function limit(int $limit) : self
     {
-        if (! is_numeric($limit)) {
-            throw new Exception\InvalidArgumentException(sprintf(
-                '%s expects parameter to be numeric, "%s" given',
-                __METHOD__,
-                (is_object($limit) ? get_class($limit) : gettype($limit))
-            ));
-        }
-
         $this->limit = $limit;
         return $this;
     }
 
-    /**
-     * @param int $offset
-     * @return self Provides a fluent interface
-     * @throws Exception\InvalidArgumentException
-     */
-    public function offset($offset)
+    public function offset(int $offset) : self
     {
-        if (! is_numeric($offset)) {
-            throw new Exception\InvalidArgumentException(sprintf(
-                '%s expects parameter to be numeric, "%s" given',
-                __METHOD__,
-                (is_object($offset) ? get_class($offset) : gettype($offset))
-            ));
-        }
-
         $this->offset = $offset;
         return $this;
     }
 
-    /**
-     * @param Select $select
-     * @param string $type
-     * @param string $modifier
-     * @return self Provides a fluent interface
-     * @throws Exception\InvalidArgumentException
-     */
-    public function combine(Select $select, $type = self::COMBINE_UNION, $modifier = '')
+    public function combine(Select $select, string $type = self::COMBINE_UNION, string $modifier = '') : self
     {
         if ($this->combine !== []) {
             throw new Exception\InvalidArgumentException(
                 'This Select object is already combined and cannot be combined with multiple Selects objects'
             );
         }
-        $this->combine = [
-            'select' => $select,
-            'type' => $type,
-            'modifier' => $modifier
-        ];
+        $this->combine = compact(self::SELECT, 'type', self::MODIFIER);
         return $this;
     }
 
-    /**
-     * @param string $part
-     * @return self Provides a fluent interface
-     * @throws Exception\InvalidArgumentException
-     */
-    public function reset($part)
+    public function reset(string $part) : self
     {
         switch ($part) {
             case self::TABLE:
@@ -463,11 +412,11 @@ public function reset($part)
     }
 
     /**
-     * @param $index
-     * @param $specification
-     * @return self Provides a fluent interface
+     * @param string       $index
+     * @param array|string $specification
+     * @return $this
      */
-    public function setSpecification($index, $specification)
+    public function setSpecification(string $index, $specification) : self
     {
         if (! method_exists($this, 'process' . $index)) {
             throw new Exception\InvalidArgumentException('Not a valid specification name.');
@@ -476,7 +425,7 @@ public function setSpecification($index, $specification)
         return $this;
     }
 
-    public function getRawState($key = null)
+    public function getRawState(?string $key = null)
     {
         $rawState = [
             self::TABLE      => $this->table,
@@ -489,57 +438,45 @@ public function getRawState($key = null)
             self::HAVING     => $this->having,
             self::LIMIT      => $this->limit,
             self::OFFSET     => $this->offset,
-            self::COMBINE    => $this->combine
+            self::COMBINE    => $this->combine,
         ];
         return (isset($key) && array_key_exists($key, $rawState)) ? $rawState[$key] : $rawState;
     }
 
-    /**
-     * Returns whether the table is read only or not.
-     *
-     * @return bool
-     */
-    public function isTableReadOnly()
+    public function isTableReadOnly() : bool
     {
         return $this->tableReadOnly;
     }
 
     protected function processStatementStart(
-        PlatformInterface $platform,
-        DriverInterface $driver = null,
-        ParameterContainer $parameterContainer = null
-    ) {
+        PlatformInterface   $platform,
+        ?DriverInterface    $driver = null,
+        ?ParameterContainer $parameterContainer = null
+    ) : ?array {
         if ($this->combine !== []) {
             return ['('];
         }
     }
 
     protected function processStatementEnd(
-        PlatformInterface $platform,
-        DriverInterface $driver = null,
-        ParameterContainer $parameterContainer = null
-    ) {
+        PlatformInterface   $platform,
+        ?DriverInterface    $driver = null,
+        ?ParameterContainer $parameterContainer = null
+    ) : ?array {
         if ($this->combine !== []) {
             return [')'];
         }
     }
 
-    /**
-     * Process the select part
-     *
-     * @param PlatformInterface $platform
-     * @param DriverInterface $driver
-     * @param ParameterContainer $parameterContainer
-     * @return null|array
-     */
     protected function processSelect(
-        PlatformInterface $platform,
-        DriverInterface $driver = null,
-        ParameterContainer $parameterContainer = null
-    ) {
+        PlatformInterface   $platform,
+        ?DriverInterface    $driver = null,
+        ?ParameterContainer $parameterContainer = null
+    ) : ?array {
         $expr = 1;
 
-        list($table, $fromTable) = $this->resolveTable($this->table, $platform, $driver, $parameterContainer);
+        [$table, $fromTable] = $this->resolveTable($this->table, $platform, $driver, $parameterContainer);
+
         // process table columns
         $columns = [];
         foreach ($this->columns as $columnIndexOrAs => $column) {
@@ -559,18 +496,19 @@ protected function processSelect(
                 $parameterContainer,
                 (is_string($columnIndexOrAs) ? $columnIndexOrAs : 'column')
             );
+
             // process As portion
             if (is_string($columnIndexOrAs)) {
                 $columnAs = $platform->quoteIdentifier($columnIndexOrAs);
             } elseif (stripos($columnName, ' as ') === false) {
-                $columnAs = (is_string($column)) ? $platform->quoteIdentifier($column) : 'Expression' . $expr++;
+                $columnAs = is_string($column) ? $platform->quoteIdentifier($column) : 'Expression' . $expr++;
             }
-            $columns[] = (isset($columnAs)) ? [$columnName, $columnAs] : [$columnName];
+            $columns[] = isset($columnAs) ? [$columnName, $columnAs] : [$columnName];
         }
 
         // process join columns
         foreach ($this->joins->getJoins() as $join) {
-            $joinName = (is_array($join['name'])) ? key($join['name']) : $join['name'];
+            $joinName = is_array($join['name']) ? key($join['name']) : $join['name'];
             $joinName = parent::resolveTable($joinName, $platform, $driver, $parameterContainer);
 
             foreach ($join['columns'] as $jKey => $jColumn) {
@@ -606,44 +544,49 @@ protected function processSelect(
 
         if (! isset($table)) {
             return [$columns];
-        } elseif (isset($quantifier)) {
+        }
+
+        if (isset($quantifier)) {
             return [$quantifier, $columns, $table];
-        } else {
-            return [$columns, $table];
         }
+
+        return [$columns, $table];
     }
 
     protected function processJoins(
-        PlatformInterface $platform,
-        DriverInterface $driver = null,
-        ParameterContainer $parameterContainer = null
+        PlatformInterface   $platform,
+        ?DriverInterface    $driver = null,
+        ?ParameterContainer $parameterContainer = null
     ) {
         return $this->processJoin($this->joins, $platform, $driver, $parameterContainer);
     }
 
     protected function processWhere(
-        PlatformInterface $platform,
-        DriverInterface $driver = null,
-        ParameterContainer $parameterContainer = null
+        PlatformInterface   $platform,
+        ?DriverInterface    $driver = null,
+        ?ParameterContainer $parameterContainer = null
     ) {
-        if ($this->where->count() == 0) {
+        if ($this->where->count() === 0) {
             return;
         }
+
         return [
-            $this->processExpression($this->where, $platform, $driver, $parameterContainer, 'where')
+            $this->processExpression($this->where, $platform, $driver, $parameterContainer, self::WHERE)
         ];
     }
 
     protected function processGroup(
-        PlatformInterface $platform,
-        DriverInterface $driver = null,
-        ParameterContainer $parameterContainer = null
+        PlatformInterface   $platform,
+        ?DriverInterface    $driver = null,
+        ?ParameterContainer $parameterContainer = null
     ) {
         if ($this->group === null) {
             return;
         }
+
         // process table columns
         $groups = [];
+
         foreach ($this->group as $column) {
             $groups[] = $this->resolveColumnValue(
                 [
@@ -660,25 +603,25 @@ protected function processGroup(
     }
 
     protected function processHaving(
-        PlatformInterface $platform,
-        DriverInterface $driver = null,
-        ParameterContainer $parameterContainer = null
+        PlatformInterface   $platform,
+        ?DriverInterface    $driver = null,
+        ?ParameterContainer $parameterContainer = null
     ) {
-        if ($this->having->count() == 0) {
+        if ($this->having->count() === 0) {
             return;
         }
         return [
-            $this->processExpression($this->having, $platform, $driver, $parameterContainer, 'having')
+            $this->processExpression($this->having, $platform, $driver, $parameterContainer, self::HAVING)
         ];
     }
 
     protected function processOrder(
-        PlatformInterface $platform,
-        DriverInterface $driver = null,
-        ParameterContainer $parameterContainer = null
-    ) {
+        PlatformInterface   $platform,
+        ?DriverInterface    $driver = null,
+        ?ParameterContainer $parameterContainer = null
+    ) : ?array {
         if (empty($this->order)) {
-            return;
+            return null;
         }
         $orders = [];
         foreach ($this->order as $k => $v) {
@@ -690,7 +633,7 @@ protected function processOrder(
             }
             if (is_int($k)) {
                 if (strpos($v, ' ') !== false) {
-                    list($k, $v) = preg_split('# #', $v, 2);
+                    [$k, $v] = preg_split('# #', $v, 2);
                 } else {
                     $k = $v;
                     $v = self::ORDER_ASCENDING;
@@ -707,85 +650,71 @@ protected function processOrder(
 
     protected function processLimit(
         PlatformInterface $platform,
-        DriverInterface $driver = null,
-        ParameterContainer $parameterContainer = null
+        ?DriverInterface $driver = null,
+        ?ParameterContainer $parameterContainer = null
     ) {
         if ($this->limit === null) {
             return;
         }
         if ($parameterContainer) {
             $paramPrefix = $this->processInfo['paramPrefix'];
-            $parameterContainer->offsetSet($paramPrefix . 'limit', $this->limit, ParameterContainer::TYPE_INTEGER);
-            return [$driver->formatParameterName($paramPrefix . 'limit')];
+            $parameterContainer->offsetSet($paramPrefix . self::LIMIT, $this->limit, ParameterContainer::TYPE_INTEGER);
+            return [$driver->formatParameterName($paramPrefix . self::LIMIT)];
         }
-        return [$platform->quoteValue($this->limit)];
+        return [$platform->quoteValue((string) $this->limit ?? '')];
     }
 
     protected function processOffset(
         PlatformInterface $platform,
-        DriverInterface $driver = null,
-        ParameterContainer $parameterContainer = null
+        ?DriverInterface $driver = null,
+        ?ParameterContainer $parameterContainer = null
     ) {
         if ($this->offset === null) {
             return;
         }
         if ($parameterContainer) {
             $paramPrefix = $this->processInfo['paramPrefix'];
-            $parameterContainer->offsetSet($paramPrefix . 'offset', $this->offset, ParameterContainer::TYPE_INTEGER);
-            return [$driver->formatParameterName($paramPrefix . 'offset')];
+            $parameterContainer->offsetSet($paramPrefix . self::OFFSET, $this->offset, ParameterContainer::TYPE_INTEGER);
+            return [$driver->formatParameterName($paramPrefix . self::OFFSET)];
         }
 
-        return [$platform->quoteValue($this->offset)];
+        return [$platform->quoteValue((string) $this->offset ?? '')];
     }
 
     protected function processCombine(
         PlatformInterface $platform,
-        DriverInterface $driver = null,
-        ParameterContainer $parameterContainer = null
+        ?DriverInterface $driver = null,
+        ?ParameterContainer $parameterContainer = null
     ) {
-        if ($this->combine == []) {
+        if ($this->combine === []) {
             return;
         }
 
         $type = $this->combine['type'];
-        if ($this->combine['modifier']) {
-            $type .= ' ' . $this->combine['modifier'];
+        if ($this->combine[self::MODIFIER]) {
+            $type .= ' ' . $this->combine[self::MODIFIER];
         }
 
         return [
             strtoupper($type),
-            $this->processSubSelect($this->combine['select'], $platform, $driver, $parameterContainer),
+            $this->processSubSelect($this->combine[self::SELECT], $platform, $driver, $parameterContainer),
         ];
     }
 
-    /**
-     * Variable overloading
-     *
-     * @param  string $name
-     * @throws Exception\InvalidArgumentException
-     * @return mixed
-     */
-    public function __get($name)
+    public function __get(string $name)
     {
         switch (strtolower($name)) {
-            case 'where':
+            case self::WHERE:
                 return $this->where;
-            case 'having':
+            case self::HAVING:
                 return $this->having;
-            case 'joins':
+            case self::JOINS:
                 return $this->joins;
             default:
                 throw new Exception\InvalidArgumentException('Not a valid magic property for this object');
         }
     }
 
-    /**
-     * __clone
-     *
-     * Resets the where object each time the Select is cloned.
-     *
-     * @return void
-     */
     public function __clone()
     {
         $this->where  = clone $this->where;
@@ -795,16 +724,16 @@ public function __clone()
 
     /**
      * @param string|TableIdentifier|Select $table
-     * @param PlatformInterface $platform
-     * @param DriverInterface $driver
-     * @param ParameterContainer $parameterContainer
-     * @return string
+     * @param PlatformInterface             $platform
+     * @param DriverInterface               $driver
+     * @param ParameterContainer            $parameterContainer
+     * @return array
      */
     protected function resolveTable(
         $table,
-        PlatformInterface $platform,
-        DriverInterface $driver = null,
-        ParameterContainer $parameterContainer = null
+        PlatformInterface   $platform,
+        ?DriverInterface    $driver = null,
+        ?ParameterContainer $parameterContainer = null
     ) {
         $alias = null;
 
@@ -830,7 +759,7 @@ protected function resolveTable(
 
         return [
             $table,
-            $fromTable
+            $fromTable,
         ];
     }
 }
diff --git a/src/Sql/Sql.php b/src/Sql/Sql.php
index 2cc1428204..f8fb8a2803 100644
--- a/src/Sql/Sql.php
+++ b/src/Sql/Sql.php
@@ -1,62 +1,66 @@
 <?php
 /**
- * Zend Framework (http://framework.zend.com/)
- *
- * @link      http://github.com/zendframework/zf2 for the canonical source repository
- * @copyright Copyright (c) 2005-2016 Zend Technologies USA Inc. (http://www.zend.com)
- * @license   http://framework.zend.com/license/new-bsd New BSD License
+ * @see       https://github.com/zendframework/zend-db for the canonical source repository
+ * @copyright Copyright (c) 2005-2019 Zend Technologies USA Inc. (https://www.zend.com)
+ * @license   https://github.com/zendframework/zend-db/blob/master/LICENSE.md New BSD License
  */
 
+declare(strict_types=1);
+
 namespace Zend\Db\Sql;
 
 use Zend\Db\Adapter\AdapterInterface;
 use Zend\Db\Adapter\Driver\StatementInterface;
 use Zend\Db\Adapter\Platform\PlatformInterface;
+use Zend\Db\Sql\Platform\AbstractPlatform;
+use function is_array;
+use function is_string;
+
 
 class Sql
 {
     /** @var AdapterInterface */
-    protected $adapter = null;
+    protected $adapter;
 
     /** @var string|array|TableIdentifier */
-    protected $table = null;
+    protected $table;
 
     /** @var Platform\Platform */
-    protected $sqlPlatform = null;
+    protected $sqlPlatform;
 
     /**
      * @param AdapterInterface                  $adapter
      * @param null|string|array|TableIdentifier $table
-     * @param null|Platform\AbstractPlatform    $sqlPlatform @deprecated since version 3.0
+     * @param null|AbstractPlatform             $sqlPlatform @deprecated since version 3.0
      */
-    public function __construct(AdapterInterface $adapter, $table = null, Platform\AbstractPlatform $sqlPlatform = null)
-    {
+    public function __construct(
+        AdapterInterface           $adapter,
+        $table = null,
+        ?AbstractPlatform $sqlPlatform = null
+    ) {
         $this->adapter = $adapter;
         if ($table) {
             $this->setTable($table);
         }
-        $this->sqlPlatform = $sqlPlatform ?: new Platform\Platform($adapter);
+        $this->sqlPlatform = $sqlPlatform ?? new Platform\Platform($adapter);
     }
 
-    /**
-     * @return null|\Zend\Db\Adapter\AdapterInterface
-     */
-    public function getAdapter()
+    public function getAdapter() : ?AdapterInterface
     {
         return $this->adapter;
     }
 
-    public function hasTable()
+    public function hasTable() : bool
     {
         return ($this->table !== null);
     }
 
     /**
      * @param string|array|TableIdentifier $table
-     * @return self Provides a fluent interface
+     * @return $this
      * @throws Exception\InvalidArgumentException
      */
-    public function setTable($table)
+    public function setTable($table) : self
     {
         if (is_string($table) || is_array($table) || $table instanceof TableIdentifier) {
             $this->table = $table;
@@ -73,12 +77,16 @@ public function getTable()
         return $this->table;
     }
 
-    public function getSqlPlatform()
+    public function getSqlPlatform() : Platform\Platform
     {
         return $this->sqlPlatform;
     }
 
-    public function select($table = null)
+    /**
+     * @param null|string|array|TableIdentifier $table
+     * @return Select
+     */
+    public function select($table = null) : Select
     {
         if ($this->table !== null && $table !== null) {
             throw new Exception\InvalidArgumentException(sprintf(
@@ -86,10 +94,14 @@ public function select($table = null)
                 $this->table
             ));
         }
-        return new Select(($table) ?: $this->table);
+        return new Select($table ?? $this->table);
     }
 
-    public function insert($table = null)
+    /**
+     * @param null|string|TableIdentifier $table
+     * @return Insert
+     */
+    public function insert($table = null) : Insert
     {
         if ($this->table !== null && $table !== null) {
             throw new Exception\InvalidArgumentException(sprintf(
@@ -97,10 +109,14 @@ public function insert($table = null)
                 $this->table
             ));
         }
-        return new Insert(($table) ?: $this->table);
+        return new Insert($table ?? $this->table);
     }
 
-    public function update($table = null)
+    /**
+     * @param null|string|TableIdentifier $table
+     * @return Update
+     */
+    public function update($table = null) : Update
     {
         if ($this->table !== null && $table !== null) {
             throw new Exception\InvalidArgumentException(sprintf(
@@ -108,10 +124,14 @@ public function update($table = null)
                 $this->table
             ));
         }
-        return new Update(($table) ?: $this->table);
+        return new Update($table ?? $this->table);
     }
 
-    public function delete($table = null)
+    /**
+     * @param null|string|TableIdentifier $table
+     * @return Delete
+     */
+    public function delete($table = null) : Delete
     {
         if ($this->table !== null && $table !== null) {
             throw new Exception\InvalidArgumentException(sprintf(
@@ -119,23 +139,16 @@ public function delete($table = null)
                 $this->table
             ));
         }
-        return new Delete(($table) ?: $this->table);
+        return new Delete($table ?? $this->table);
     }
 
-    /**
-     * @param PreparableSqlInterface $sqlObject
-     * @param StatementInterface     $statement
-     * @param AdapterInterface       $adapter
-     *
-     * @return StatementInterface
-     */
     public function prepareStatementForSqlObject(
         PreparableSqlInterface $sqlObject,
-        StatementInterface $statement = null,
-        AdapterInterface $adapter = null
-    ) {
-        $adapter   = $adapter ?: $this->adapter;
-        $statement = $statement ?: $adapter->getDriver()->createStatement();
+        ?StatementInterface    $statement = null,
+        ?AdapterInterface      $adapter = null
+    ) : StatementInterface {
+        $adapter   = $adapter ?? $this->adapter;
+        $statement = $statement ?? $adapter->getDriver()->createStatement();
 
         return $this->sqlPlatform->setSubject($sqlObject)->prepareStatement($adapter, $statement);
     }
@@ -145,26 +158,17 @@ public function prepareStatementForSqlObject(
      *
      * @param SqlInterface           $sqlObject
      * @param PlatformInterface|null $platform
-     *
      * @return string
      *
      * @deprecated Deprecated in 2.4. Use buildSqlString() instead
      */
-    public function getSqlStringForSqlObject(SqlInterface $sqlObject, PlatformInterface $platform = null)
+    public function getSqlStringForSqlObject(SqlInterface $sqlObject, ?PlatformInterface $platform = null) : string
     {
-        $platform = ($platform) ?: $this->adapter->getPlatform();
+        $platform = $platform ?? $this->adapter->getPlatform();
         return $this->sqlPlatform->setSubject($sqlObject)->getSqlString($platform);
     }
 
-    /**
-     * @param SqlInterface     $sqlObject
-     * @param AdapterInterface $adapter
-     *
-     * @return string
-     *
-     * @throws Exception\InvalidArgumentException
-     */
-    public function buildSqlString(SqlInterface $sqlObject, AdapterInterface $adapter = null)
+    public function buildSqlString(SqlInterface $sqlObject, ?AdapterInterface $adapter = null) : string
     {
         return $this
             ->sqlPlatform
diff --git a/src/Sql/SqlInterface.php b/src/Sql/SqlInterface.php
index 551a458c98..5831f98fb8 100644
--- a/src/Sql/SqlInterface.php
+++ b/src/Sql/SqlInterface.php
@@ -1,24 +1,17 @@
 <?php
 /**
- * Zend Framework (http://framework.zend.com/)
- *
- * @link      http://github.com/zendframework/zf2 for the canonical source repository
- * @copyright Copyright (c) 2005-2016 Zend Technologies USA Inc. (http://www.zend.com)
- * @license   http://framework.zend.com/license/new-bsd New BSD License
+ * @see       https://github.com/zendframework/zend-db for the canonical source repository
+ * @copyright Copyright (c) 2005-2019 Zend Technologies USA Inc. (https://www.zend.com)
+ * @license   https://github.com/zendframework/zend-db/blob/master/LICENSE.md New BSD License
  */
 
+declare(strict_types=1);
+
 namespace Zend\Db\Sql;
 
 use Zend\Db\Adapter\Platform\PlatformInterface;
 
 interface SqlInterface
 {
-    /**
-     * Get SQL string for statement
-     *
-     * @param null|PlatformInterface $adapterPlatform
-     *
-     * @return string
-     */
-    public function getSqlString(PlatformInterface $adapterPlatform = null);
+    public function getSqlString(?PlatformInterface $adapterPlatform = null) : string;
 }
diff --git a/src/Sql/TableIdentifier.php b/src/Sql/TableIdentifier.php
index 85cb10e7f0..141f6af441 100644
--- a/src/Sql/TableIdentifier.php
+++ b/src/Sql/TableIdentifier.php
@@ -1,33 +1,30 @@
 <?php
 /**
- * Zend Framework (http://framework.zend.com/)
- *
- * @link      http://github.com/zendframework/zf2 for the canonical source repository
- * @copyright Copyright (c) 2005-2016 Zend Technologies USA Inc. (http://www.zend.com)
- * @license   http://framework.zend.com/license/new-bsd New BSD License
+ * @see       https://github.com/zendframework/zend-db for the canonical source repository
+ * @copyright Copyright (c) 2005-2019 Zend Technologies USA Inc. (https://www.zend.com)
+ * @license   https://github.com/zendframework/zend-db/blob/master/LICENSE.md New BSD License
  */
 
+declare(strict_types=1);
+
 namespace Zend\Db\Sql;
 
-/**
- */
+use function get_class;
+use function gettype;
+use function is_callable;
+use function is_object;
+use function is_string;
+use function sprintf;
+
 class TableIdentifier
 {
-    /**
-     * @var string
-     */
+    /** @var string */
     protected $table;
 
-    /**
-     * @var null|string
-     */
+    /** @var null|string */
     protected $schema;
 
-    /**
-     * @param string      $table
-     * @param null|string $schema
-     */
-    public function __construct($table, $schema = null)
+    public function __construct(string $table, ?string $schema = null)
     {
         if (! (is_string($table) || is_callable([$table, '__toString']))) {
             throw new Exception\InvalidArgumentException(sprintf(
@@ -36,7 +33,7 @@ public function __construct($table, $schema = null)
             ));
         }
 
-        $this->table = (string) $table;
+        $this->table = $table;
 
         if ('' === $this->table) {
             throw new Exception\InvalidArgumentException('$table must be a valid table name, empty string given');
@@ -52,7 +49,7 @@ public function __construct($table, $schema = null)
                 ));
             }
 
-            $this->schema = (string) $schema;
+            $this->schema = $schema;
 
             if ('' === $this->schema) {
                 throw new Exception\InvalidArgumentException(
@@ -64,36 +61,28 @@ public function __construct($table, $schema = null)
 
     /**
      * @param string $table
-     *
      * @deprecated please use the constructor and build a new {@see TableIdentifier} instead
      */
-    public function setTable($table)
+    public function setTable(string $table) : void
     {
         $this->table = $table;
     }
 
-    /**
-     * @return string
-     */
-    public function getTable()
+    public function getTable() : string
     {
         return $this->table;
     }
 
-    /**
-     * @return bool
-     */
-    public function hasSchema()
+    public function hasSchema() : bool
     {
         return ($this->schema !== null);
     }
 
     /**
-     * @param $schema
-     *
+     * @param null|string $schema
      * @deprecated please use the constructor and build a new {@see TableIdentifier} instead
      */
-    public function setSchema($schema)
+    public function setSchema(?string $schema) : void
     {
         $this->schema = $schema;
     }
@@ -101,12 +90,12 @@ public function setSchema($schema)
     /**
      * @return null|string
      */
-    public function getSchema()
+    public function getSchema() : ?string
     {
         return $this->schema;
     }
 
-    public function getTableAndSchema()
+    public function getTableAndSchema() : array
     {
         return [$this->table, $this->schema];
     }
diff --git a/src/Sql/Update.php b/src/Sql/Update.php
index 09563cf528..ca4b2b92dc 100644
--- a/src/Sql/Update.php
+++ b/src/Sql/Update.php
@@ -1,22 +1,26 @@
 <?php
 /**
- * Zend Framework (http://framework.zend.com/)
- *
- * @link      http://github.com/zendframework/zf2 for the canonical source repository
- * @copyright Copyright (c) 2005-2016 Zend Technologies USA Inc. (http://www.zend.com)
- * @license   http://framework.zend.com/license/new-bsd New BSD License
+ * @see       https://github.com/zendframework/zend-db for the canonical source repository
+ * @copyright Copyright (c) 2005-2019 Zend Technologies USA Inc. (https://www.zend.com)
+ * @license   https://github.com/zendframework/zend-db/blob/master/LICENSE.md New BSD License
  */
 
+declare(strict_types=1);
+
 namespace Zend\Db\Sql;
 
-use Zend\Db\Adapter\ParameterContainer;
-use Zend\Db\Adapter\Platform\PlatformInterface;
 use Zend\Db\Adapter\Driver\DriverInterface;
 use Zend\Db\Adapter\Driver\Pdo\Pdo;
+use Zend\Db\Adapter\ParameterContainer;
+use Zend\Db\Adapter\Platform\PlatformInterface;
 use Zend\Stdlib\PriorityList;
+use function implode;
+use function is_numeric;
+use function is_string;
+use function sprintf;
+use function strtolower;
 
 /**
- *
  * @property Where $where
  */
 class Update extends AbstractPreparableSql
@@ -24,55 +28,45 @@ class Update extends AbstractPreparableSql
     /**@#++
      * @const
      */
-    const SPECIFICATION_UPDATE = 'update';
-    const SPECIFICATION_SET = 'set';
-    const SPECIFICATION_WHERE = 'where';
-    const SPECIFICATION_JOIN = 'joins';
+    public const SPECIFICATION_UPDATE = 'update';
+    public const SPECIFICATION_SET = 'set';
+    public const SPECIFICATION_WHERE = 'where';
+    public const SPECIFICATION_JOIN = 'joins';
 
-    const VALUES_MERGE = 'merge';
-    const VALUES_SET   = 'set';
+    public const VALUES_MERGE = 'merge';
+    public const VALUES_SET   = 'set';
     /**@#-**/
 
     protected $specifications = [
         self::SPECIFICATION_UPDATE => 'UPDATE %1$s',
         self::SPECIFICATION_JOIN => [
             '%1$s' => [
-                [3 => '%1$s JOIN %2$s ON %3$s', 'combinedby' => ' ']
+                [3 => '%1$s JOIN %2$s ON %3$s', 'combinedby' => ' '],
             ]
         ],
         self::SPECIFICATION_SET => 'SET %1$s',
         self::SPECIFICATION_WHERE => 'WHERE %1$s',
     ];
 
-    /**
-     * @var string|TableIdentifier
-     */
+    /** @var string|TableIdentifier */
     protected $table = '';
 
-    /**
-     * @var bool
-     */
+    /** @var bool */
     protected $emptyWhereProtection = true;
 
-    /**
-     * @var PriorityList
-     */
+    /** @var PriorityList */
     protected $set;
 
-    /**
-     * @var string|Where
-     */
-    protected $where = null;
+    /** @var string|Where */
+    protected $where;
 
-    /**
-     * @var null|Join
-     */
-    protected $joins = null;
+    /** @var null|Join */
+    protected $joins;
 
     /**
      * Constructor
      *
-     * @param  null|string|TableIdentifier $table
+     * @param null|string|TableIdentifier $table
      */
     public function __construct($table = null)
     {
@@ -81,6 +75,7 @@ public function __construct($table = null)
         }
         $this->where = new Where();
         $this->joins = new Join();
+
         $this->set = new PriorityList();
         $this->set->isLIFO(false);
     }
@@ -88,10 +83,10 @@ public function __construct($table = null)
     /**
      * Specify table for statement
      *
-     * @param  string|TableIdentifier $table
-     * @return self Provides a fluent interface
+     * @param string|TableIdentifier $table
+     * @return $this
      */
-    public function table($table)
+    public function table($table) : self
     {
         $this->table = $table;
         return $this;
@@ -100,18 +95,18 @@ public function table($table)
     /**
      * Set key/value pairs to update
      *
-     * @param  array $values Associative array of key values
-     * @param  string $flag One of the VALUES_* constants
-     * @return self Provides a fluent interface
+     * @param array  $values Associative array of key values
+     * @param string $flag One of the VALUES_* constants
+     * @return $this
      * @throws Exception\InvalidArgumentException
      */
-    public function set(array $values, $flag = self::VALUES_SET)
+    public function set(array $values, string $flag = self::VALUES_SET) : self
     {
         if ($values === null) {
             throw new Exception\InvalidArgumentException('set() expects an array of values');
         }
 
-        if ($flag == self::VALUES_SET) {
+        if ($flag === self::VALUES_SET) {
             $this->set->clear();
         }
         $priority = is_numeric($flag) ? $flag : 0;
@@ -127,12 +122,12 @@ public function set(array $values, $flag = self::VALUES_SET)
     /**
      * Create where clause
      *
-     * @param  Where|\Closure|string|array $predicate
-     * @param  string $combination One of the OP_* constants from Predicate\PredicateSet
-     * @return self Provides a fluent interface
+     * @param Where|\Closure|string|array $predicate
+     * @param string                      $combination One of the OP_* constants from Predicate\PredicateSet
+     * @return $this
      * @throws Exception\InvalidArgumentException
      */
-    public function where($predicate, $combination = Predicate\PredicateSet::OP_AND)
+    public function where($predicate, string $combination = Predicate\PredicateSet::OP_AND) : self
     {
         if ($predicate instanceof Where) {
             $this->where = $predicate;
@@ -145,20 +140,20 @@ public function where($predicate, $combination = Predicate\PredicateSet::OP_AND)
     /**
      * Create join clause
      *
-     * @param  string|array $name
-     * @param  string $on
-     * @param  string $type one of the JOIN_* constants
-     * @return self Provides a fluent interface
+     * @param string|array $name
+     * @param string       $on
+     * @param string       $type one of the JOIN_* constants
+     * @return $this
      * @throws Exception\InvalidArgumentException
      */
-    public function join($name, $on, $type = Join::JOIN_INNER)
+    public function join($name, string $on, string $type = Join::JOIN_INNER) : self
     {
         $this->joins->join($name, $on, [], $type);
 
         return $this;
     }
 
-    public function getRawState($key = null)
+    public function getRawState(?string $key = null)
     {
         $rawState = [
             'emptyWhereProtection' => $this->emptyWhereProtection,
@@ -171,9 +166,9 @@ public function getRawState($key = null)
     }
 
     protected function processUpdate(
-        PlatformInterface $platform,
-        DriverInterface $driver = null,
-        ParameterContainer $parameterContainer = null
+        PlatformInterface   $platform,
+        ?DriverInterface    $driver = null,
+        ?ParameterContainer $parameterContainer = null
     ) {
         return sprintf(
             $this->specifications[static::SPECIFICATION_UPDATE],
@@ -182,9 +177,9 @@ protected function processUpdate(
     }
 
     protected function processSet(
-        PlatformInterface $platform,
-        DriverInterface $driver = null,
-        ParameterContainer $parameterContainer = null
+        PlatformInterface   $platform,
+        ?DriverInterface    $driver = null,
+        ?ParameterContainer $parameterContainer = null
     ) {
         $setSql = [];
         $i      = 0;
@@ -226,11 +221,11 @@ protected function processSet(
     }
 
     protected function processWhere(
-        PlatformInterface $platform,
-        DriverInterface $driver = null,
-        ParameterContainer $parameterContainer = null
+        PlatformInterface   $platform,
+        ?DriverInterface    $driver = null,
+        ?ParameterContainer $parameterContainer = null
     ) {
-        if ($this->where->count() == 0) {
+        if ($this->where->count() === 0) {
             return;
         }
         return sprintf(
@@ -240,9 +235,9 @@ protected function processWhere(
     }
 
     protected function processJoins(
-        PlatformInterface $platform,
-        DriverInterface $driver = null,
-        ParameterContainer $parameterContainer = null
+        PlatformInterface   $platform,
+        ?DriverInterface    $driver = null,
+        ?ParameterContainer $parameterContainer = null
     ) {
         return $this->processJoin($this->joins, $platform, $driver, $parameterContainer);
     }
@@ -252,26 +247,19 @@ protected function processJoins(
      *
      * Proxies to "where" only
      *
-     * @param  string $name
+     * @param string $name
      * @return mixed
      */
-    public function __get($name)
+    public function __get(string $name)
     {
-        if (strtolower($name) == 'where') {
+        if (strtolower($name) === 'where') {
             return $this->where;
         }
     }
 
-    /**
-     * __clone
-     *
-     * Resets the where object each time the Update is cloned.
-     *
-     * @return void
-     */
     public function __clone()
     {
         $this->where = clone $this->where;
-        $this->set = clone $this->set;
+        $this->set   = clone $this->set;
     }
 }
diff --git a/src/Sql/Where.php b/src/Sql/Where.php
index 68166d5256..6be0074da8 100644
--- a/src/Sql/Where.php
+++ b/src/Sql/Where.php
@@ -1,12 +1,12 @@
 <?php
 /**
- * Zend Framework (http://framework.zend.com/)
- *
- * @link      http://github.com/zendframework/zf2 for the canonical source repository
- * @copyright Copyright (c) 2005-2016 Zend Technologies USA Inc. (http://www.zend.com)
- * @license   http://framework.zend.com/license/new-bsd New BSD License
+ * @see       https://github.com/zendframework/zend-db for the canonical source repository
+ * @copyright Copyright (c) 2005-2019 Zend Technologies USA Inc. (https://www.zend.com)
+ * @license   https://github.com/zendframework/zend-db/blob/master/LICENSE.md New BSD License
  */
 
+declare(strict_types=1);
+
 namespace Zend\Db\Sql;
 
 class Where extends Predicate\Predicate