Mysql的Event

Mysql的Event

Event简介

Event是mysql中的一个事件，和触发器类似，触发器是在某条sql语句执行后可能会触发，而Event是每隔一段时间或某个特定的时间点执行，可以精确到秒。

准备

在创建Event前，需要将mysql中的event_scheduler属性设置为ON。

使用命令

mysql> show variables like "%event_scheduler%";
+-----------------+-------+
| Variable_name   | Value |
+-----------------+-------+
| event_scheduler | OFF   |
+-----------------+-------+
1 row in set (0.19 sec)

mysql> set global event_scheduler = on;
Query OK, 0 rows affected (0.04 sec)

mysql> show variables like "%event_scheduler%";
+-----------------+-------+
| Variable_name   | Value |
+-----------------+-------+
| event_scheduler | ON   |
+-----------------+-------+
1 row in set (0.06 sec)

创建Event

语法格式

create event event_name on schedule
[at time][every interval]
do event_body;

interval: 
    quantity {YEAR | QUARTER | MONTH | DAY | HOUR | MINUTE | 
              WEEK | SECOND | YEAR_MONTH | DAY_HOUR | DAY_MINUTE | 
              DAY_SECOND | HOUR_MINUTE | HOUR_SECOND | MINUTE_SECOND} 

示例：每1分钟在ADMIN表中插入一条数据。

首先创建一个存储过程

delimiter //
create procedure aminute(in in_id int)
begin
insert into ADMIN(id,user_id,traveldate,fee,days)  values(in_id,@@hostname,now(),100,10);
end//
delimiter;

然后创建一个Event

create event insert_minute
on schedule
every 1 minute
do call aminute(floor(rand()*10000000+1));

运行结果

查看Event

查看当前database的Event

mysql> show events;
+-----+---------------+---------+-----------+-----------+------------+----------------+----------------+---------------------+------+---------+------------+----------------------+----------------------+--------------------+
| Db  | Name          | Definer | Time zone | Type      | Execute at | Interval value | Interval field | Starts              | Ends | Status  | Originator | character_set_client | collation_connection | Database Collation |
+-----+---------------+---------+-----------+-----------+------------+----------------+----------------+---------------------+------+---------+------------+----------------------+----------------------+--------------------+
| DB1 | insert_minute | root@%  | SYSTEM    | RECURRING | NULL       | 1              | MINUTE         | 2019-11-26 10:32:58 | NULL | ENABLED |          1 | utf8mb4              | utf8mb4_general_ci   | utf8_general_ci    |
+-----+---------------+---------+-----------+-----------+------------+----------------+----------------+---------------------+------+---------+------------+----------------------+----------------------+--------------------+
1 row in set (0.73 sec)

mysql> 

修改Event

使用Alter命令

alter event event_name on schedule
[at time][every interval][rename to newname]
do event_body;

比如，将上面的示例修改为每秒插入一条，并修改Event的名称

alter event insert_minute on schedule every 1 second rename to insert_second do call aminute(floor(rand()*10000000+1));

运行结果

删除Event

使用drop命令

drop event event_name;

示例：

mysql> show events;
+-----+---------------+---------+-----------+-----------+------------+----------------+----------------+---------------------+------+---------+------------+----------------------+----------------------+--------------------+
| Db  | Name          | Definer | Time zone | Type      | Execute at | Interval value | Interval field | Starts              | Ends | Status  | Originator | character_set_client | collation_connection | Database Collation |
+-----+---------------+---------+-----------+-----------+------------+----------------+----------------+---------------------+------+---------+------------+----------------------+----------------------+--------------------+
| DB1 | insert_second | root@%  | SYSTEM    | RECURRING | NULL       | 1              | SECOND         | 2019-11-26 10:49:20 | NULL | ENABLED |          1 | utf8mb4              | utf8mb4_general_ci   | utf8_general_ci    |
+-----+---------------+---------+-----------+-----------+------------+----------------+----------------+---------------------+------+---------+------------+----------------------+----------------------+--------------------+
1 row in set (0.15 sec)

mysql> drop event insert_second;
Query OK, 0 rows affected (0.09 sec)

mysql> show events;
Empty set