MySQL5.1.x版本中引入了一项新特性EVENT,顾名思义就是事件、定时任务机制,在指定的时间单元内执行特定的任务,因此今后一些对数据定时性操作不再依赖外部程序,而直接使用数据库本身提供的功能。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=1my.ini or my.cnf 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 '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 ‘comment’]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 '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;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 EXISTSDROP EVENT IF EXISTS e_test; |