ROLLBACK — abort the current transaction
ROLLBACK [ WORK | TRANSACTION ] [ AND [ NO ] CHAIN ]
   ROLLBACK rolls back the current transaction and causes
   all the updates made by the transaction to be discarded.
  
WORKTRANSACTION #Optional key words. They have no effect.
AND CHAIN #
      If AND CHAIN is specified, a new (not aborted)
      transaction is immediately started with the same transaction
      characteristics (see SET TRANSACTION) as the
      just finished one.  Otherwise, no new transaction is started.
     
   Use COMMIT to
   successfully terminate a transaction.
  
   Issuing ROLLBACK outside of a transaction
   block emits a warning and otherwise has no effect.  ROLLBACK AND
   CHAIN outside of a transaction block is an error.
  
To abort all changes:
ROLLBACK;
   The command ROLLBACK conforms to the SQL standard.  The
   form ROLLBACK TRANSACTION is a PostgreSQL extension.