MySQL计划任务(事件调度器) Event Scheduler介绍

要查看当前是否已开启事件调度器，可执行如下SQL

SHOW VARIABLES LIKE 'event_scheduler';
或

SELECT @@event_scheduler;
或

SHOW PROCESSLIST;
若显示

+-----------------+-------+
| Variable_name   | Value |
+-----------------+-------+
| event_scheduler | OFF   |
+-----------------+-------+
则可执行

SET GLOBAL event_scheduler = 1;
或

SET GLOBAL event_scheduler = ON;
来开启，也可以直接在启动命令加上“–event_scheduler=1”，例如

mysqld ... --event_scheduler=1

my.ini or my.f 中的
[mysqld]
添加 event_scheduler=ON

创建事件(CREATE EVENT)
先来看一下它的语法

CREATE EVENT [IF NOT EXISTS] event_name
ON SCHEDULE schedule
[ON COMPLETION [NOT] PRESERVE]
[ENABLE | DISABLE]
[COMMENT 'ment']
DO sql_statement;

schedule:
AT TIMESTAMP [+ INTERVAL INTERVAL]
| EVERY INTERVAL [STARTS TIMESTAMP] [ENDS TIMESTAMP]

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

1)来看一个简单的例子来演示每秒插入一条记录到数据表

USE test;
CREATE TABLE aaa (timeline TIMESTAMP);
CREATE EVENT e_test_insert
ON SCHEDULE EVERY 1 SECOND
DO INSERT INTO test.aaa VALUES (CURRENT_TIMESTAMP);
等待3秒钟后，再执行查询成功。

2) 5天后清空test表

CREATE EVENT e_test
ON SCHEDULE AT CURRENT_TIMESTAMP + INTERVAL 5 DAY
DO TRUNCATE TABLE test.aaa;

3) 2007年7月20日12点整清空test表

CREATE EVENT e_test
ON SCHEDULE AT TIMESTAMP '2007-07-20 12:00:00'
DO TRUNCATE TABLE test.aaa;

4) 每天定时清空test表

CREATE EVENT e_test
ON SCHEDULE EVERY 1 DAY
DO TRUNCATE TABLE test.aaa;

5) 5天后开启每天定时清空test表

CREATE EVENT e_test
ON SCHEDULE EVERY 1 DAY
STARTS CURRENT_TIMESTAMP + INTERVAL 5 DAY
DO TRUNCATE TABLE test.aaa;

6) 每天定时清空test表，5天后停止执行

CREATE EVENT e_test
ON SCHEDULE EVERY 1 DAY
ENDS CURRENT_TIMESTAMP + INTERVAL 5 DAY
DO TRUNCATE TABLE test.aaa;

7) 5天后开启每天定时清空test表，一个月后停止执行

CREATE EVENT e_test
ON SCHEDULE EVERY 1 DAY
STARTS CURRENT_TIMESTAMP + INTERVAL 5 DAY
ENDS CURRENT_TIMESTAMP + INTERVAL 1 MONTH
DO TRUNCATE TABLE test.aaa;
[ON COMPLETION [NOT] PRESERVE]可以设置这个事件是执行一次还是持久执行，默认为NOT PRESERVE。

8) 每天定时清空test表(只执行一次，任务完成后就终止该事件)

CREATE EVENT e_test
ON SCHEDULE EVERY 1 DAY
ON COMPLETION NOT PRESERVE
DO TRUNCATE TABLE test.aaa;
[ENABLE | DISABLE]可是设置该事件创建后状态是否开启或关闭，默认为ENABLE。
[COMMENT ‘ment']可以给该事件加上注释。

修改事件(ALTER EVENT)
ALTER EVENT event_name
[ON SCHEDULE schedule]
[RENAME TO new_event_name]
[ON COMPLETION [NOT] PRESERVE]
[COMMENT 'ment']
[ENABLE | DISABLE]
[DO sql_statement]
1) 临时关闭事件

ALTER EVENT e_test DISABLE;

2) 开启事件

ALTER EVENT e_test ENABLE;
3) 将每天清空test表改为5天清空一次

ALTER EVENT e_test
ON SCHEDULE EVERY 5 DAY;

删除事件(DROP EVENT)
语法很简单，如下所示

DROP EVENT [IF EXISTS] event_name
例如删除前面创建的e_test事件

DROP EVENT e_test;
前提是这个事件存在，否则会产生ERROR 1513 (HY000): Unknown event错误，最好加上IF EXISTS

DROP EVENT IF EXISTS e_test;