1) SHOW VARIABLES LIKE ‘event_scheduler’;
2) SELECT @@event_scheduler;
3) SHOW PROCESSLIST;(是否有State为:Waiting for next activation的进程,User为event_scheduler)
时间调度器是否开启由全局变量event_scheduler决定,它有三个可以设定的值: – OFF : 事件调度器是关闭的,调度线程并没有运行,并且在SHOW PROCESSLIST中不显示,默认值是OFF – ON :事件调度器是开启的,调度线程并没有运行,并且执行所有的调度事件,通过SHOW PROCESSLIST可以查看Waiting for next activation的进程 – DISABLED : 设定这个值表示Event Scheduler是被禁止的,无法在Mysql运行状态下改变其值
注:在Mysql启动时如果在my.cnf设置了event_scheduler=ON(OFF or 1 or 0)时,就不能在运行时修改撑DISABLED,如果设置event_scheduler=DISABLED时,就不能在运行时修改其值为ON ( OFF or 1 or 0)
mysql> SELECT @@event_scheduler;+-------------------+| @@event_scheduler |+-------------------+| DISABLED |+-------------------+1 row in set (0.00 sec)mysql> SET @@global.event_scheduler = 1;ERROR 1290 (HY000): The MySQL server is running with the --event-scheduler=DISABLED or --skip-grant-tables option so it cannot execute this statement在mysql运行时开启Event(4种方法均可):SET GLOBAL event_scheduler = ON;SET @@global.event_scheduler = ON;SET GLOBAL event_scheduler = 1;SET @@global.event_scheduler = 1;在mysql运行时关闭Event(4种方法均可):SET GLOBAL event_scheduler = OFF;SET @@global.event_scheduler = OFF;SET GLOBAL event_scheduler = 0;SET @@global.event_scheduler = 0;
语法: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 event_body;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}
说明:
DEFINER默认是CREATE EVENT的用户,可以理解为DEFINER=CURRENT_USER,指该event的用户,服务器在执行该事件时,使用该用户来检查权限;如果设置语法:‘user_name’@‘host_name’,如果当前CREATE EVENT用户没有supser权限,则无法将该event指派给其他用户;如果有super权限,则可以指定任意存在的用户,若不存在,时间执行时报错
IF NOT EXISTS : 如果在同一个schema创建一个已经存在的event_name时不会做任何操作,也不会出错,但会出现warings:该event已经存在;如果不增加此关键词已经存在的话提示ERROR: 1537 (HY000): Event ‘countsum’ already exists
ON SCHEDULE :用于设置什么时间执行,执行的频率及执行多久的问题
AT timestamp :表示在给定的datetime或者timestamp的时间执行一次
+ INTERVAL interval:表示从AT timestamp多久之后执行
EVERY interval :有规律的重复执行
[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。
event创建时间的3周2天后:AT CURRENT_TIMESTAMP + INTERVAL 3 WEEK + INTERVAL 2 DAY2分钟10秒:+ INTERVAL '2:10' MINUTE_SECOND每6周:EVERY 6 WEEK从现在开始30分钟后每12小时执行一次到从现在到4周后结束执行:EVERY 12 HOUR STARTS CURRENT_TIMESTAMP + INTERVAL 30 MINUTE ENDS CURRENT_TIMESTAMP + INTERVAL 4 WEEK
实例:
前提:创建EVENT的用户需要只少对应schema的EVENT权限
最基本的create event只需要三个部分:
1. create event关键字以及一个event名称
2. on schedule子句
3. do子句
1. 在创建事件myevent1小时后执行,执行一条更新CREATE EVENT myevent ON SCHEDULE AT CURRENT_TIMESTAMP + INTERVAL 1 HOURDO UPDATE myschema.mytable SET mycol = mycol + 1;2.2014年3月20日12点整清空test表:CREATE EVENT e_test ON SCHEDULE AT TIMESTAMP '2014-03-20 12:00:00' DO TRUNCATE TABLE test.aaa;3.5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;4.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;5.5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;6.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;[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。
ALTER [DEFINER = { user | CURRENT_USER }] EVENT event_name [ON SCHEDULE schedule] [ON COMPLETION [NOT] PRESERVE] [RENAME TO new_event_name] [ENABLE | DISABLE | DISABLE ON SLAVE] [COMMENT 'comment'] [DO event_body]
说明:
对于任何一个拥有定义在database里面事件的event权限的用户都可以修改event,并且成功需改后,那个用户就会成为此event的definer
实例:CREATE EVENT myevent ON SCHEDULE EVERY 6 HOUR COMMENT 'A sample comment.' DO UPDATE myschema.mytable SET mycol = mycol + 1;将上面的event从开始之后每6个小时执行一次改为从开始4个小时后每12小时执行一次只修改scheduleALTER EVENT myevent ON SCHEDULE EVERY 12 HOUR STARTS CURRENT_TIMESTAMP + INTERVAL 4 HOUR;同时修改schedule和bodyALTER EVENT myevent ON SCHEDULE AT CURRENT_TIMESTAMP + INTERVAL 1 DAY DO TRUNCATE TABLE myschema.mytable;
关闭、启动、别名、移动、删除event:
临时关闭某个eventALTER EVENT myevent DISABLE;开启某个eventALTER EVENT myevent ENABLE;别名某个eventALTER EVENT olddb.myeventRENAME TO newdb.myevent;将myevent从olddb库移动到newdb库ALTER EVENT olddb.myeventRENAME TO newdb.myevent;删除eventDROP EVENT [IF EXISTS] event_name
Event信息相关表:
information_schema.events
mysql.event
查看事件的创建信息
show create event countsum \G
查看sem库的events信息
USE sem;
SHOW EVENTS \G
SHOW EVENTS FROM sem;
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