例子 :当年龄大于18的时候能插入否者报错
delimiter //
create trigger age_tri before insert
on tri_test for each row
begin
declare msg varchar(200);
if (new.age < 18) then
set msg = "Age must be greater than 18";
signal sqlstate 'LY000' SET message_text = msg;
end if;
end //
delimiter ;
解析:delimiter // 从新定义语句结束符为“//”
create trigger age_tri 创建触发器age_tri
before insert 在插入之前
begin 开始
declare msg varchar(200) 声明变量为200个字符以内的msg
if (new.age<18)then 判断条件为你想插入的数据<18爆出以下错误:
在报错的时候:ERROR 1644 (LY000): Age must be greater than 18
end if; 结束判断
end// 结束触发器
delimiter ; 从新定义语句结束符为";"
用处:create [definer = { user | current_user}] trigger trigger_name
before|after insert|update|delete
on tbl_name
for each row
查看触发器:
select * from information_schema.triggers ;
删除触发器:
drop trigger [if exists] [schema_name.]trigger_name;
注意:当你执行drop table时,表上的触发器也被drop掉了