SQL TRUNCATE TABLE Statement

In this tutorial you will learn how to quickly delete all rows from a table using SQL.

Removing Table Data

The TRUNCATE TABLE statement removes all the rows from a table more quickly than a DELETE. Logically, TRUNCATE TABLE is similar to the DELETE statement with no WHERE clause.

The TRUNCATE TABLE statement removes all the rows from a table, but the table structure and its columns, constraints, indexes, and so on remain intact. To remove the table definition in addition to its data, you can use the DROP TABLE statement.

Syntax

The basic syntax of TRUNCATE TABLE can be given with:

Let's perform the truncate operation on a database table.

Consider we've an employees table in our database with the following records:

+--------+--------------+------------+--------+---------+
| emp_id | emp_name     | hire_date  | salary | dept_id |
+--------+--------------+------------+--------+---------+
|      1 | Ethan Hunt   | 2001-05-01 |   5000 |       4 |
|      2 | Tony Montana | 2002-07-15 |   6500 |       1 |
|      3 | Sarah Connor | 2005-10-18 |   8000 |       5 |
|      4 | Rick Deckard | 2007-01-03 |   7200 |       3 |
|      5 | Martin Blank | 2008-06-24 |   5600 |    NULL |
+--------+--------------+------------+--------+---------+

The following command removes all the rows from the employees table:

TRUNCATE TABLE employees;

Now, after executing the above SQL statement, if you try to select the records from the employees table, you will get an empty result set.

TRUNCATE TABLE vs DELETE

Although DELETE and TRUNCATE TABLE seem to have the same effect, but they do work differently. Here are some major differences between these two statements:

• TRUNCATE TABLE statement drop and re-create the table in such a way that any
  auto-increment value is reset to its start value which is generally 1.
• DELETE lets you filter which rows to be deleted based upon an optional WHERE clause, whereas TRUNCATE TABLE doesn't support WHERE clause it just removes all the rows.
• TRUNCATE TABLE is faster and uses fewer system resources than DELETE, because DELETE scans the table to generate a count of rows that were affected then delete the rows one by one and records an entry in the database log for each deleted row, while TRUNCATE TABLE just delete all the rows without providing any additional information.