MySQL存储过程，事务回滚

CREATE PROCEDURE p1(idd int)
BEGIN
DECLARE EXIT HANDLER FOR SQLEXCEPTION,SQLWARNING,NOT FOUND
  BEGIN
  ROLLBACK;
  END;
SET @comId = idd ;
START TRANSACTION;
 DELETE FROM tb_aa WHERE id=@comId;
 DELETE FROM tb_bb WHERE id=@comId;
COMMIT;
END