MS SQL Truncate Table vs Delete - SQL

Introduction

When it comes to deleting data from a SQL Server database, there are two common options: TRUNCATE TABLE and DELETE. Although both commands can be used to remove data from a table, there are differences in their behavior and usage.

TRUNCATE TABLE

TRUNCATE TABLE is a DDL (Data Definition Language) command that is used to remove all the data from a table in the shortest possible time. Unlike DELETE, which removes data row by row, TRUNCATE TABLE empties the table by deallocating the data pages used by the table. This means that the transaction log file size remains smaller and the process is faster. It is important to note that TRUNCATE TABLE cannot be used on tables that have a foreign key relationship with other tables, and it cannot be rolled back once executed.

Syntax

TRUNCATE TABLE table_name;

Example

TRUNCATE TABLE Customers;

DELETE

DELETE is a DML (Data Manipulation Language) command that is used to remove data row by row from a table. It can be used on tables that have a foreign key relationship with other tables, and it can be rolled back if necessary. DELETE is slower than TRUNCATE TABLE because it logs each row deletion in the transaction log, which can cause the transaction log file to grow larger.

Syntax

DELETE FROM table_name [WHERE condition];

Example

DELETE FROM Customers WHERE CustomerID = 1;

Conclusion

Knowing the differences between TRUNCATE TABLE and DELETE is important when choosing the appropriate command for removing data from a SQL Server database. TRUNCATE TABLE is faster and cannot be rolled back, while DELETE is slower but can be rolled back if necessary. It is recommended to use TRUNCATE TABLE for large tables with no foreign key relationships and DELETE for smaller tables or tables with foreign key relationships.