MySQL- 30触发器实战:给新用户发邮件-CFANZ编程社区

什么是触发器

触发器(trigger)用于监视某种情况并触发某种操作，它是与表事件相关的特殊的存储过程，它的执行不是由程序调用，而是由事件来触发。例如，当对某张表进行insert、delete、update操作时就会触发执行它。

#创建触发器语法
CREATE TRIGGER trigger_name trigger_time trigger_event ON table_name FOR EACH ROW

参数说明:

trigger_name:触发器名称
trigger_time:触发时间，取值有before、after trigger_event:触发事件，取值有insert、update、delete table_name:触发器监控的表名
trigger_stmt:触发执行的语句，可以使用OLD、NEW来引用变化前后的记录内容

NEW.columnName:获取INSERT触发事件中新插入的数据
OLD.columnName:获取UPDATE和DELETE触发事件中被更新、删除的数据

测试数据及需求描述

当有新用户插入时，自动给用户发送邮件

drop table if exists user_info; 
drop table if exists email_info;
create table user_info(
  id int not null auto_increment primary key, 
  name varchar(30),
  email varchar(50)
);

insert into user_info(id, name, email) values(1, 'zhangsan', 'zhangsan@qq.com'); 
insert into user_info(id, name, email) values(2, 'lisi', 'lisi@qq.com');

create table email_info(
  id int not null auto_increment primary key, 
  email varchar(50),
  content text,
  send_time datetime
);

触发器实战:给新用户发邮件

# 触发器实战:给新用户发邮件
delimiter //
// 触发时间 监控的表名
CREATE TRIGGER send_email_trigger AFTER INSERT ON user_info FOR EACH ROW 
BEGIN
// 获取新插入的数据
insert into email_info(email, content, send_time) values(NEW.email, 'welcome to mysql team! ', now()); 
END
// delimiter ;

实战案例

创建表数据

mysql> select * from user_info;
+----+----------+-----------------+
| id | name     | email           |
+----+----------+-----------------+
|  1 | zhangsan | zhangsan@qq.com |
|  2 | lisi     | lisi@qq.com     |
+----+----------+-----------------+
2 rows in set (0.00 sec)

mysql> select * from email_info;
+----+-----------------+------------------------+---------------------+
| id | email           | content                | send_time           |
+----+-----------------+------------------------+---------------------+
|  1 | zhangsan@qq.com | welcome to mysql team  | 2020-06-06 00:19:25 |
|  2 | zhangsan@qq.com | welcome to mysql team! | 2020-06-06 00:24:39 |
|  3 | zhangsan@qq.com | welcome to mysql team! | 2020-06-06 00:26:26 |
|  4 | lisi@qq.com     | welcome to mysql team! | 2020-06-06 00:26:33 |
+----+-----------------+------------------------+---------------------+
4 rows in set (0.00 sec)

创建触发器

mysql> delimiter //
mysql> CREATE TRIGGER send_email_trigger AFTER INSERT ON user_info FOR EACH ROW 
    -> BEGIN
    -> insert into email_info(email, content, send_time) values(NEW.email, 'welcome to mysql team! ', now()); 
    -> END
    -> //
Query OK, 0 rows affected (0.02 sec)

插入数据

mysql> insert into user_info(id, name, email) values(3, 'st', 'st@qq.com');
    -> //
Query OK, 1 row affected (0.01 sec)

mysql> delimiter ;
mysql> select * from email_info;
+----+-----------------+-------------------------+---------------------+
| id | email           | content                 | send_time           |
+----+-----------------+-------------------------+---------------------+
|  1 | zhangsan@qq.com | welcome to mysql team   | 2020-06-06 00:19:25 |
|  2 | zhangsan@qq.com | welcome to mysql team!  | 2020-06-06 00:24:39 |
|  3 | zhangsan@qq.com | welcome to mysql team!  | 2020-06-06 00:26:26 |
|  4 | lisi@qq.com     | welcome to mysql team!  | 2020-06-06 00:26:33 |
|  5 | st@qq.com       | welcome to mysql team!  | 2020-06-06 00:45:31 |
+----+-----------------+-------------------------+---------------------+
5 rows in set (0.00 sec)

删除触发器

mysql> drop TRIGGER send_email_trigger;
Query OK, 0 rows affected (0.01 sec)