14.mysql 基础之触发器

定义语法createtrigger名称before/after insert/update/delete on 表名begin触发器执行语句end准备数据一create table empasselect id,name,salary from emploee准备数据二create table emp_backasselect * from emp where 121新建触发器实现插入数据后往备份库也插入数据create trigger insert_emp_messageafter insert on empfor each rowbegininsert into emp_back values(new.id,new.name,new.salary);end验证insert into emp values(202,piter,3000)select * from empselect * from emp_back2新建触发器实现数据删除前往备份库也插入数据create trigger delete_emp_messagebefore delete on empfor each rowbegininsert into emp_back values(old.id,old.name,old.salary);end验证delete from emp where id201select * from empselect * from emp_back3查看触发器show create trigger insert_emp_messageshow triggers;4删除触发器drop trigger delete_emp_message注1触发器的优点是保持数据的完整性缺点是表结构修改后容易忘记触发器事件导致报错后排查问题复杂。 工作中根据具体情况使用。