SQL TRUNCATE TABLE

The TRUNCATE TABLE statement in SQL is a powerful command used to swiftly remove all rows from a table, leaving the table structure intact. This operation is often favored over the DELETE statement for its efficiency, especially when dealing with large datasets.

In this article, We will learn about SQL TRUNCATE TABLE in detail with the help of various examples and so on.

SQL TRUNCATE TABLE

• The TRUNCATE TABLE statement in SQL is used to quickly remove all rows from a table, effectively emptying the table.
  
• Unlike the DELETE statement, which removes rows one at a time and can be rolled back (depending on the database support for transactions).
  
• TRUNCATE TABLE is usually more efficient because it deallocates the data pages used by the table, rather than performing individual row deletions.

Note: The TRUNCATE command can not be used to Truncate a Column or Database in SQL.

Syntax

TRUNCATE TABLE Syntax is:

TRUNCATE TABLE table_name;

Example of SQL TRUNCATE TABLE

Let's understand TRUNCATE in SQL with examples. Here we will look at different examples of the SQL TRUNCATE TABLE command.

First, we will create a demo SQL database and table, on which we will use the TRUNCATE TABLE command.

CREATE DATABASE GEEKSFORGEEKS;
USE GEEKSFORGEEKS;
CREATE TABLE EMPLOYEE(
    EMP_ID INT(4),
    NAME VARCHAR(20),
    AGE INT(3),
    DOB DATE,
    SALARY DECIMAL(7,2));
INSERT INTO EMPLOYEE VALUES(121,'AJAY KUMAR',23,'1987-09-12',23456.32);
INSERT INTO EMPLOYEE VALUES(132,'BOBBY DEOL',34,'1989-02-19',84164.56);
INSERT INTO EMPLOYEE VALUES(246,'ELVISH SMITH',27,'1996-01-29',51876.97);
INSERT INTO EMPLOYEE VALUES(955,'GEORGE CLARKE',31,'1992-09-21',91451.64);
INSERT INTO EMPLOYEE VALUES(729,'MONICA GELLER',28,'1985-11-18',98329.43);

The following table will be created.

Example of TRUNCATE TABLE in SQL

In this example, we will Truncate the created table.

Query:

TRUNCATE TABLE EMPLOYEE;

Output:

After truncating data of our table, the data of our table has been erased but the structure is preserved so now if we perform SELECT * FROM EMPLOYEE command on our table we will see everything is erased and an empty set is being returned.

But let's now check whether the structure of the table is deleted or it has been preserved so we again use the DESC command to see the structure of the table and we will see that the structure remains as it is.

SQL TRUNCATE vs DELETE

Here's a comparison of the TRUNCATE and DELETE statements in SQL presented in a tabular format:

This table should help clarify the differences between TRUNCATE TABLE and DELETE

SQL TRUNCATE vs DROP

Here's a comparison of the SQL TRUNCATE TABLE and DROP TABLE commands in a tabular format:

Important Points About SQL TRUNCATE TABLE

• TRUNCATE TABLE is used to empty a table by removing all rows, but it retains the table structure.
• TRUNCATE TABLE is ideal for quickly removing all data from a table without deleting the table structure, making it efficient for data cleanup operations
• TRUNCATE TABLE is faster and uses fewer system and transaction logs compared to DELETE.
• However, TRUNCATE TABLE typically cannot be rolled back if executed within a transaction.

Conclusion

In conclusion, the TRUNCATE TABLE command is a highly efficient method for quickly removing all rows from a table while preserving its structure. It is particularly useful in scenarios where you need to clear a table without deleting it, offering a performance advantage over the DELETE statement due to minimal transaction logging.