【mysql】四、mysql的学习---触发器

-- 触发器是与表有关的数据库对象，指在insert/update/delete之前或之后，触发并执行触发器中定义的sql语句集合。触发器的这种特性可以协助应用在数据库端确保数据的完整性，日志记录，数据校验等操作。

-- 使用别名OLD和NEW来应用触发器中发生变化的记录内容，这与其它的数据库是相似的。现在触发器还只支持行级触发，不支持语句级触发。

-- 建表sql

create table emp_logs(
id int(11) not null auto_increment,
opertation varchar(20) not null comment‘操作类型:inset/update/delete‘ ,
opertate_time datetime not null comment‘操作时间‘ ,
opertate_id int(11) not null comment‘操作表的ID‘ ,
opertate_params varchar(500) comment‘操作参数‘ ,
primary key(id)
)engine=innodb default charset=utf8;

drop trigger if exists emp_insert_trigger;
delimiter $
create trigger emp_insert_trigger
after insert 
on emp
for each row
begin
  insert into emp_logs(id,opertation,opertate_time,opertate_id,opertate_params) 
  values(null,‘insert‘,now(),new.id,concat(‘插入后(id:‘,new.id,‘,name:‘,new.name,‘,age:‘,new.age,‘,salary:‘,new.salary,‘)‘));
end$
delimiter ;

insert into emp(id,name,age,salary) values(null,‘光明左使‘,30,3500);
select * from emp_logs;

drop trigger if exists emp_update_trigger;
delimiter $
create trigger emp_update_trigger
after update 
on emp
for each row
begin

insert into emp_logs(id,opertation,opertate_time,opertate_id,opertate_params) 
values(null,‘update‘,now(),new.id,concat(‘修改前(id:‘,old.id,‘,name:‘,old.name,‘,age:‘,old.age,‘,salary:‘,old.salary,‘)‘,
‘ 修改后(id:‘,new.id,‘,name:‘,new.name,‘,age:‘,new.age,‘,salary:‘,new.salary,‘)‘));

end$
delimiter ;

update emp set age=39 where id=3;
select * from emp_logs;

drop trigger if exists emp_delete_trigger;
delimiter $
create trigger emp_delete_trigger
after delete 
on emp
for each row
begin

insert into emp_logs(id,opertation,opertate_time,opertate_id,opertate_params) 
values(null,‘delete‘,now(),old.id,concat(‘删除前(id:‘,old.id,‘,name:‘,old.name,‘,age:‘,old.age,‘,salary:‘,old.salary,‘)‘));

end$
delimiter ;

delete from emp where id=4;
select * from emp_logs;

show triggers

drop trigger test.emp_delete_trigger