Understanding the differences between the SQL Server DELETE and TRUNCATE commands is essential for any database administrator. While both commands can be used to delete data from a table, there are some key differences between them. The TRUNCATE command is a DDL command that removes all rows from the table, while the DELETE statement is a DML command that can have a WHERE clause to delete specific records. TRUNCATE is faster than DELETE as it uses less of the transaction log, and it also re-seeds identity values while deleting does not.
Additionally, TRUNCATE does not activate triggers, while DELETE does. When deleting all records from a table, it is preferable to use TRUNCATE instead of DELETE as it is faster and more efficient. However, if you have a foreign key constraint that references the table you are trying to truncate, it will not work even if the reference table contains no data. Additionally, TRUNCATE does not record any information, but it does record the demapping of the data page of the table in which TRUNCATE was activated.
Therefore, if you need to perform some automatic cleaning or logging action when deleting rows, TRUNCATE should never be used.