mysql 触发器介绍

create trigger triggerName
after/before insert/update/delete on tableName
for each row --这句话在mysql是固定的
begin
sql语句;
end;

如下在插入之前自动生成座位号

DROP TRIGGER IF EXISTS `pxlb_zwh_insert`;
CREATE TRIGGER `pxlb_zwh_insert`
BEFORE INSERT ON `dj_pxlb`
FOR EACH ROW
begin
IF new.zwh IS NULL OR new.zwh < 1 THEN
     SET new.zwh = (select IFNULL(max(t1.zwh),0)+1 from `dj_pxlb` as t1 where t1.ccbh=new.ccbh);
END IF;
end;

DROP TRIGGER IF EXISTS t_make_data;
CREATE TRIGGER t_make_data
BEFORE INSERT ON t_tab1
FOR EACH ROW
BEGIN
DECLARE number_rand BIGINT(20) DEFAULT 4000 ; --声明变量
SET number_rand = (SELECT CAST(RAND()*300+300 AS signed) AS rand);
SET new.number_rand = number_rand;
END;

巴特西

mysql 触发器介绍

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