Added Difference Between Delete And Truncate Commands In Sql

Author: code-atom

_posts/2025-08-04-difference-between-delete-and-truncate-commands-in-sql.markdown

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+---
+title: Difference Between DELETE and TRUNCATE Commands In SQL
+date: 2025-08-04 14:18:00 +05:30
+categories:
+- database
+tags:
+- sql
+layout: post
+---
+
+# **What is a DELETE command?**
+
+- The DELETE statement is a **DML command (Data Manipulation Language).** It is used to delete single or multiple rows (records) from a table.
+- The **WHERE** clause in DELETE command **defines a condition** for deleting only the selected unwanted rows from the target table.
+- The DELETE query creates a log file in the transaction log. It stores the records before deleting them. So, in case, we delete one or many important rows, we can get them back using the **ROLLBACK** command.
+- Since the DELETE statement is a DML command, we have to commit the changes manually. Point to remember, the **ROLLBACK must be done before COMMIT**.
+
+### **Syntax:**
+
+> DELETE FROM table_name WHERE condition;
+> 
+
+# **What is a TRUNCATE command?**
+
+- The TRUNCATE command is a **DDL command** **(Data Definition Language).** We use this command on tables to delete all the records at once.
+- The TRUNCATE command **does not use any condition,** like a WHERE clause to define a condition. So, we should use it only when all the data in the target table is unwanted.
+- The TRUNCATE command uses table lock to **lock the table and page** for truncate operation, instead of row lock. So, it only logs the deallocation of the pages that store the records, and as a result, it takes much less time than the DELETE command.
+- Since the TRUNCATE command is a DDL command, the **commit is automatically done** here.
+- The TRUNCATE command **resets the identity** to its seed value.
+
+**Seed value**: seed value in SQL refers to the internal value which the Server uses to generate the next value.
+
+### **Syntax:**
+
+> TRUNCATE TABLE table_name;
+> 
+
+# **"TRUNCATE cannot be rolled back" - Fact or Myth?**
+
+We know the DELETE command can use rollback. But, many people have a misconception that the TRUNCATE statements cannot use rollback. It is **MYTH**!
+
+**Myth**: The truncate command works so fast that it does not have time to log its records in the transaction log.
+
+**Fact:** It **only logs the deallocation of the page of stored records**, so the work is **faster than the DELETE** command.
+
+Meanwhile, the DELETE statement logs all the rows of the table, so, the DELETE statement takes much more time than the TRUNCATE command.
+
+In conclusion, the TRUNCATE command can be rolled back for truncated records inside the transaction.
+
+> Page: It is the fundamental unit of data storage in SQL Server.
+> 
+
+**DELETE vs TRUNCATE**
+
+| Topic | DELETE | TRUNCATE |
+| --- | --- | --- |
+| Definition | DELETE is a SQL command that **removes one or multiple rows from a table using conditions.** | TRUNCATE is a SQL command that **removes all the rows** from a table without using any condition. |
+| Language | It is a **DML(Data Manipulation Language)** command. | It is a **DDL(Data Definition Language)** command. |
+| Commit | We have to manually COMMIT the changes in the DELETE command. | The changes are automatically COMMIT in the TRUNCATE command. |
+| Process | It deletes rows **one by one with conditions.** | It deletes **all the data at once**. |
+| Condition | It uses the **WHERE clause** as a condition. | It does not take any condition i.e. **does not use WHERE clause.** |
+| Lock | It **locks all the rows** for deletion. | It uses table lock to **lock the pages** for deletion. |
+| Log | It **logs every single record in the transaction log**. | It **only logs the deallocation of the pages where the data is stored.** |
+| Transaction space | It uses **more transaction space** compared to the TRUNCATION command. | It uses **less transaction space** compared to the DELETE command. |
+| Identity | It does **not reset the table identity** to its seed value if there is an identity column. | It **resets** the table identity to its seed value. |
+| Permission | It needs **delete** permission. | It needs **alter** table permission. |
+| Speed | It is much **slower** when comes to big databases. | It is faster or in other words, **instant**. |