diff --git a/src/Builder/ArrayMergeBuilder.php b/src/Builder/ArrayMergeBuilder.php
index 29eb4644..a603c8a4 100644
--- a/src/Builder/ArrayMergeBuilder.php
+++ b/src/Builder/ArrayMergeBuilder.php
@@ -42,21 +42,17 @@ final class ArrayMergeBuilder extends MultiOperandFunctionBuilder
     protected function buildFromExpression(MultiOperandFunction $expression, array &$params): string
     {
         $operandType = $this->buildOperandType($expression->getType());
-        $selects = [];
+        $builtOperands = [];
 
         foreach ($expression->getOperands() as $operand) {
-            $builtOperand = $this->buildOperand($operand, $params);
-
-            $selects[] = "SELECT value FROM JSON_TABLE($builtOperand, '$[*]' COLUMNS(value $operandType PATH '$')) AS t";
+            $builtOperands[] = $this->buildOperand($operand, $params);
         }
 
-        $unions = implode(' UNION ', $selects);
-
-        if ($expression->getOrdered()) {
-            $unions .= ' ORDER BY value';
-        }
+        $orderBy = $expression->getOrdered() ? ' ORDER BY value' : '';
 
-        return '(SELECT JSON_ARRAYAGG(value) AS value FROM (' . $unions . ') AS t)';
+        return "(SELECT JSON_ARRAYAGG(DISTINCT value$orderBy) AS value"
+            . ' FROM JSON_TABLE(JSON_MERGE_PRESERVE(' . implode(', ', $builtOperands) . '),'
+            . " '$[*]' COLUMNS(value $operandType PATH '$')) AS t)";
     }
 
     private function buildOperandType(string|ColumnInterface $type): string
diff --git a/tests/Provider/QueryBuilderProvider.php b/tests/Provider/QueryBuilderProvider.php
index 096a50a3..eb35dc04 100644
--- a/tests/Provider/QueryBuilderProvider.php
+++ b/tests/Provider/QueryBuilderProvider.php
@@ -360,10 +360,8 @@ public static function multiOperandFunctionBuilder(): array
         $data['ArrayMerge with 2 operands'] = [
             ArrayMerge::class,
             ["'[1,2,3]'", $stringParam],
-            '(SELECT JSON_ARRAYAGG(value) AS value FROM ('
-            . "SELECT value FROM JSON_TABLE('[1,2,3]', '$[*]' COLUMNS(value json PATH '$')) AS t"
-            . " UNION SELECT value FROM JSON_TABLE(:qp0, '$[*]' COLUMNS(value json PATH '$')) AS t"
-            . ') AS t)',
+            '(SELECT JSON_ARRAYAGG(DISTINCT value) AS value'
+            . " FROM JSON_TABLE(JSON_MERGE_PRESERVE('[1,2,3]', :qp0), '$[*]' COLUMNS(value json PATH '$')) AS t)",
             [1, 2, 3, 4, 5],
             [':qp0' => $stringParam],
         ];
@@ -373,12 +371,9 @@ public static function multiOperandFunctionBuilder(): array
             $data['ArrayMerge with 4 operands'] = [
                 ArrayMerge::class,
                 ["'[1,2,3]'", [5, 6, 7], $stringParam, self::getDb()->select(new ArrayValue([9, 10]))],
-                '(SELECT JSON_ARRAYAGG(value) AS value FROM ('
-                . "SELECT value FROM JSON_TABLE('[1,2,3]', '$[*]' COLUMNS(value json PATH '$')) AS t"
-                . " UNION SELECT value FROM JSON_TABLE(:qp0, '$[*]' COLUMNS(value json PATH '$')) AS t"
-                . " UNION SELECT value FROM JSON_TABLE(:qp1, '$[*]' COLUMNS(value json PATH '$')) AS t"
-                . " UNION SELECT value FROM JSON_TABLE((SELECT :qp2), '$[*]' COLUMNS(value json PATH '$')) AS t"
-                . ') AS t)',
+                '(SELECT JSON_ARRAYAGG(DISTINCT value) AS value'
+                . " FROM JSON_TABLE(JSON_MERGE_PRESERVE('[1,2,3]', :qp0, :qp1, (SELECT :qp2)),"
+                . " '$[*]' COLUMNS(value json PATH '$')) AS t)",
                 [1, 2, 3, 4, 5, 6, 7, 9, 10],
                 [
                     ':qp0' => new Param('[5,6,7]', DataType::STRING),
diff --git a/tests/QueryBuilderTest.php b/tests/QueryBuilderTest.php
index 0ff74f26..e78bb2a0 100644
--- a/tests/QueryBuilderTest.php
+++ b/tests/QueryBuilderTest.php
@@ -835,11 +835,9 @@ public function testArrayMergeWithTypeWithOrdering(
         $params = [];
 
         $this->assertSame(
-            '(SELECT JSON_ARRAYAGG(value) AS value FROM ('
-            . "SELECT value FROM JSON_TABLE('[2,1,3]', '$[*]' COLUMNS(value $operandType PATH '$')) AS t"
-            . " UNION SELECT value FROM JSON_TABLE(:qp0, '$[*]' COLUMNS(value $operandType PATH '$')) AS t"
-            . " UNION SELECT value FROM JSON_TABLE(:qp1, '$[*]' COLUMNS(value $operandType PATH '$')) AS t"
-            . ' ORDER BY value) AS t)',
+            '(SELECT JSON_ARRAYAGG(DISTINCT value ORDER BY value) AS value'
+            . " FROM JSON_TABLE(JSON_MERGE_PRESERVE('[2,1,3]', :qp0, :qp1),"
+            . " '$[*]' COLUMNS(value $operandType PATH '$')) AS t)",
             $qb->buildExpression($arrayMerge, $params)
         );
         Assert::arraysEquals(