mysql-触发器处理表字段的唯一性
delimiter $$ DROP TRIGGER IF EXISTS tri_nis_billhead_before_insert $$ CREATE TRIGGER tri_nis_billhead_before_insert BEFORE INSERT ON nis_billhead FOR EACH ROW BEGIN declare counts int; select count(1) into counts from nis_billhead where out_sys_bill_no=new.out_sys_bill_no; if counts >0 then SIGNAL SQLSTATE 'HY000' SET MESSAGE_TEXT='外部系统单号重复'; end if; END $$ delimiter ;