MySQL的触发器

目录

创建触发器

new与old

查看触发器

删除触发器

---

创建触发器

-- 数据准备
create database if not exists mydb10_trigger;
use mydb10_trigger;
 
-- 用户表
create table user(
    uid int primary key ,
    username varchar(50) not null,
    password varchar(50) not null
);
-- 用户信息操作日志表
create table user_logs(
    id int primary key auto_increment,
    time timestamp,
    log_text varchar(255)
);
-- 如果触发器存在，则先删除
drop trigger if  exists trigger_test1;
 
-- 创建触发器trigger_test1
create trigger trigger_test1
after insert on user -- 触发时机：当添加user表数据时触发
for each row
insert into user_logs values(NULL,now(), '有新用户注册');
 
-- 添加数据，触发器自动执行并添加日志代码
insert into user values(1,'张三','123456');

-- 如果触发器trigger_test2存在，则先删除
drop trigger if exists trigger_test2;

-- 创建触发器trigger_test2
delimiter $$
create trigger trigger_test2
after update on user  -- 触发时机：当修改user表数据时触发
for each row -- 每一行
begin
insert into user_logs values(NULL,now(), '用户修改发生了修改');
end $$
 
delimiter ;
 
-- 添加数据，触发器自动执行并添加日志代码
update user set password = '888888' where uid = 1;

new与old

create trigger trigger_test3 after insert
on user for each row
insert into user_logs values(NULL,now(),concat('有新用户添加，信息为:',NEW.uid,NEW.username,NEW.password));
 
-- 测试
insert into user values(4,'赵六','123456');

查看触发器

show triggers;

删除触发器

-- drop trigger [if exists] trigger_name 
drop trigger if exists trigger_test1;