MySQL 5_1新特性 - 事件调度器(Event Scheduler)

创建EVENT非常简单,语法如下：


CREATE
[DEFINER = { user | CURRENT_USER }]
EVENT
[IF NOT EXISTS]
event_name
ON SCHEDULE schedule
[ON COMPLETION [NOT] PRESERVE]
[ENABLE | DISABLE | DISABLE ON SLAVE]
[COMMENT 'comment']
DO sql_statement;
schedule:
AT timestamp [+ INTERVAL interval]
| EVERY interval
[STARTS timestamp [+ INTERVAL interval]]
[ENDS timestamp [+ INTERVAL interval]]
interval:
quantity {YEAR | QUARTER | MONTH | DAY | HOUR | MINUTE |
WEEK | SECOND | YEAR_MONTH | DAY_HOUR | DAY_MINUTE |
DAY_SECOND | HOUR_MINUTE | HOUR_SECOND | MINUTE_SECOND}




例如创建一个每30秒清空tableA数据的任务

CREATE EVENT E_DELETE_ASO_TOKEN ON SCHEDULE EVERY 30 SECOND DO DELETE FROM tableA ;

默认EVENT支持是没有启动的，可以通过下面的命令来查看状态：

Select @@event_scheduler;

如果返回OFF，则需要执行下面的命令启动：

SET GLOBAL event_scheduler = ON;

好了，上面虽然启动了EVENT，但是每次重启mysql之后EVENT并没有自动启动，

那么如何让它自动启动呢？

方法之一：找到当前使用的.cnf文件，在[mysqld]的下面加入如下行...

event_scheduler=1


方法二：启动mysql的时候增加--event_scheduler=1

mysql start --event_scheduler=1

事件详细语法事例(EVENT)

1>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 'comment']
    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) 首先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，再执行查询看看：

mysql> SELECT * FROM aaa;
+---------------------+
| timeline            |
+---------------------+
| 2007-07-18 20:44:26 |
| 2007-07-18 20:44:27 |
| 2007-07-18 20:44:28 |
+---------------------+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 ‘comment’]可以给该事件加上注释。

2>修改事件(ALTER EVENT)
ALTER EVENT event_name
    [ON SCHEDULE schedule]
    [RENAME TO new_event_name]
    [ON COMPLETION [NOT] PRESERVE]
    [COMMENT 'comment']
    [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;3>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;当然前提是这个事件存在，否则会产生ERROR 1513 (HY000): Unknown event错误，因此最好加上IF EXISTS

DROP EVENT IF EXISTS e_test;