ROLLBACK — abort the current transaction
ROLLBACK [ WORK | TRANSACTION ]
   ROLLBACK rolls back the current transaction and causes
   all the updates made by the transaction to be discarded.
  
WORKTRANSACTIONOptional key words. They have no effect.
Use COMMIT to successfully terminate a transaction.
   Issuing ROLLBACK outside of a transaction
   block emits a warning and otherwise has no effect.
  
To abort all changes:
ROLLBACK;
   The SQL standard only specifies the two forms
   ROLLBACK and ROLLBACK
   WORK. Otherwise, this command is fully conforming.