Triggers in MySQL

Data preparation

create database if not exists mydb10_trigger; 
use mydb10_trigger;
--  User table 
create table user(
uid int primary key ,
username varchar(50) not null,
 password varchar(50) not null 
 );
--  User information operation log table 
create table user_logs(
id int primary key auto_increment, 
time timestamp,
log_text varchar(255)
);

1. When user Add a row of data to the table , stay user_log Add logging to

--  Defining triggers ：
create TRIGGER trigger_test1 after insert
on user for each row 
insert into user_logs values(NULL,now(),' New users added ');



insert into user values(1,' Zhang San ','123456');

2. When user Add a row to the table to modify , stay user_log Add logging to

--  Defining triggers ：
delimiter $$
create TRIGGER trigger_test3 before update
on user for each row 
begin
insert into user_logs values(NULL,now(),' Modified by new users ');
end $$
delimiter;

--  modify user Data in 
update user set password = '8888'where uid = 1;
 
-- NEW

create TRIGGER trigger_test4 after insert
on user for each row 
insert into user_logs values(NULL,now(),concat(' New users added , The message is ：',NEW.uid,NEW.username,NEW.password));


insert into user values(2,' Li Si ','123456');

update Type of trigger

-- OLD
create TRIGGER trigger_test5 after update
on user for each row 
insert into user_logs values(NULL,now(),concat(' Modified by new users , The message is ：',OLD.uid,OLD.username,OLD.password));

update user set password = '88888'where uid = 2;

-- new

create TRIGGER trigger_test4 after insert
on user for each row 
insert into user_logs values(NULL,now(),concat(' New users added , The message is ：',NEW.uid,NEW.username,NEW.password));

delete Type of trigger

create TRIGGER trigger_test4 after delete
on user for each row 
insert into user_logs values(NULL,now(),concat(' Some users have been deleted , The message is ：',OLD.uid,OLD.username,OLD.password));

Delete trigger ：

drop trigger if exists trigger_test1;