DELETE and TRUNCATE

Both `DELETE` and `TRUNCATE` are SQL statements used to remove data from a table, but they differ in terms of their functionality, behavior, and usage. Here are the key differences between `DELETE` and `TRUNCATE`

DELETE

1. Functionality

   - `DELETE` is a DML (Data Manipulation Language) statement used to remove rows from a table based on a specified condition in the WHERE clause.

2. Granularity

   - You can use `DELETE` to remove specific rows based on a condition or delete all rows from a table.

3. Rollback

   - `DELETE` can be rolled back, meaning you can undo the changes made by a `DELETE` statement if a transaction is rolled back.

4. Transaction Logging

   - Each row deleted by the `DELETE` statement is logged individually, making it possible to recover individual changes in the event of a failure.

5. Usage

   - `DELETE` is typically used when you need to selectively remove specific rows based on certain criteria.

TRUNCATE

1. Functionality

   - `TRUNCATE` is a DDL (Data Definition Language) statement used to remove all rows from a table.

2. Granularity

   - `TRUNCATE` removes all rows from a table, and you cannot use a `WHERE` clause to specify conditions for deletion.

3. Rollback

   - Unlike `DELETE`, `TRUNCATE` cannot be rolled back. Once the `TRUNCATE` statement is executed, the data is permanently removed from the table.

4. Transaction Logging

   - `TRUNCATE` is generally faster than `DELETE` because it does not log individual row deletions. Instead, it deallocates the data pages, making it more efficient for large-scale removal of data.

5. Usage

   - `TRUNCATE` is commonly used when you want to quickly remove all rows from a table without considering individual conditions.

Summary

- Use `DELETE` when you need to selectively remove specific rows based on a condition or when you want to delete individual rows.

- Use `TRUNCATE` when you want to remove all rows from a table and do not need to specify conditions for deletion. `TRUNCATE` is more efficient for bulk removal of data.

Example

-- Using DELETE to remove specific rows

DELETE FROM your_table WHERE condition;

-- Using TRUNCATE to remove all rows from a table

TRUNCATE TABLE your_table;

It's important to choose the appropriate statement based on your specific requirements and the nature of the operation you want to perform.