ROLLBACK [ WORK | TRANSACTION ]
A pair of optional noise keywords. They can be ignored, or used to make your SQL more readable.
Use ROLLBACK to abort a transaction in progress and discard all changes either already made or queued to be made on COMMIT.
The following example demonstrates how to rollback an accidental delete performed within a transaction block:
booktown=# BEGIN WORK; BEGIN booktown=# DELETE FROM shipments; DELETE 36 booktown=# ROLLBACK WORK; ROLLBACK