The TRUNCATE TABLE statement is a powerful tool for deleting all the data from a table. It is much faster than the DELETE statement and does not register or lock all rows. This means that the truncated table cannot be restored, nor can it have a where clause in the SQL statement. Truncate also has the ability to reset the seed to its initial value.
When truncating, triggers are not triggered either, and all foreign key constraints must be deleted or disabled. To delete the table definition in addition to its data, you can use the DROP TABLE statement. To remove foreign key constraints, you need to run ALTER TABLE DROP FOREIGN KEY. Unfortunately, disabling restrictions is not enough.
If there are no transactions that block the table schema, the TRUNCATE TABLE command will end almost instantly. You cannot truncate a table that has foreign key constraints. When dealing with large tables, it is important to note that you cannot truncate a table that has foreign key constraints. You would need to write a script to remove the constraints, then truncate the table, and then re-create the constraints.
In PostgreSQL, you need the TRUNCATE privilege; in SQL Server, the minimum permission is the ALTER table; in MySQL, you need the DROP privilege. If you accidentally executed a TRUNCATE statement and you have a full database backup, since no changes occurred after the table was truncated, you can simply recover the data by overwriting the original database with the backup copy. In conclusion, it is important to understand how truncating tables works and its restrictions before executing any commands. It is also important to note that if there are any foreign keys that reference it, SQL Server will not allow a truncation, only a deletion.
