OLD.upc THEN IF EXISTS (SELECT 1 FROM releases WHERE upc = NEW.upc) THEN SET error_msg = CONCAT('Cannot update: upc value ', NEW.upc, ' already exists in releases.upc'); SIGNAL SQLSTATE '45000' SET MESSAGE_TEXT = error_msg; END IF; END IF; END;; ]]> OLD.upc THEN IF EXISTS (SELECT 1 FROM release_spatial WHERE upc = NEW.upc) THEN SET error_msg = CONCAT('Cannot update: upc value ', NEW.upc, ' already exists in release_spatial.upc'); SIGNAL SQLSTATE '45000' SET MESSAGE_TEXT = error_msg; END IF; END IF; END;; ]]>