富贵资源网 Design By www.hznty.com
本文实例讲述了mysql事件之修改事件（ALTER EVENT）、禁用事件（DISABLE）、启用事件（ENABLE）、事件重命名及数据库事件迁移操作。分享给大家供大家参考，具体如下：
我们要知道，MySQL允许我们更改现有事件的各种属性。如果我们要更改现有事件，可以使用ALTER EVENT语句，如下所示：
ALTER EVENT event_name ON SCHEDULE schedule ON COMPLETION [NOT] PRESERVE RENAME TO new_event_name ENABLE | DISABLE DO event_body
ALTER EVENT语句仅适用于存在的事件，如果我们尝试修改不存在的事件，MySQL将会发出一条错误消息，因此在更改事件之前，应先使用SHOW EVENTS语句检查事件的存在：
mysql> SHOW EVENTS FROM testdb; +--------+---------------+----------------+-----------+----------+---------------------+----------------+----------------+--------+------+----------+------------+----------------------+----------------------+--------------------+ | Db | Name | Definer | Time zone | Type | Execute at | Interval value | Interval field | Starts | Ends | Status | Originator | character_set_client | collation_connection | Database Collation | +--------+---------------+----------------+-----------+----------+---------------------+----------------+----------------+--------+------+----------+------------+----------------------+----------------------+--------------------+ | testdb | test_event_02 | root@localhost | SYSTEM | ONE TIME | 2017-08-03 04:24:48 | NULL | NULL | NULL | NULL | DISABLED | 0 | utf8 | utf8_general_ci | utf8_general_ci | +--------+---------------+----------------+-----------+----------+---------------------+----------------+----------------+--------+------+----------+------------+----------------------+----------------------+--------------------+ 1 row in set
创建一个每分钟将一条新记录插入到messages表中的示例事件来演示如何使用ALTER EVENT语句的各种功能：
USE testdb;
CREATE EVENT test_event_04
ON SCHEDULE EVERY 1 MINUTE
DO
INSERT INTO messages(message,created_at)
VALUES('Test ALTER EVENT statement',NOW());
我们来把事件修改为为每2分钟运行一次：
ALTER EVENT test_event_04 ON SCHEDULE EVERY 2 MINUTE;
我们还可以通过指定新的逻辑来更改事件的主体代码：
ALTER EVENT test_event_04
DO
INSERT INTO messages(message,created_at)
VALUES('Message from event',NOW());
-- 清空表中的数据
truncate messages;
修改完成后，可以等待2分钟，再次查看messages表：
mysql> SELECT * FROM messages; +----+--------------------+---------------------+ | id | message | created_at | +----+--------------------+---------------------+ | 1 | Message from event | 2017-08-03 04:46:47 | | 2 | Message from event | 2017-08-03 04:48:47 | +----+--------------------+---------------------+ 2 rows in set
我们可以在ALTER EVENT语句之后使用DISABLE关键字来禁用某个事件：
ALTER EVENT test_event_04 DISABLE;
我们也可以通过使用SHOW EVENTS语句来查看事件的状态：
mysql> SHOW EVENTS FROM testdb; +--------+---------------+----------------+-----------+-----------+---------------------+----------------+----------------+---------------------+------+----------+------------+----------------------+----------------------+--------------------+ | Db | Name | Definer | Time zone | Type | Execute at | Interval value | Interval field | Starts | Ends | Status | Originator | character_set_client | collation_connection | Database Collation | +--------+---------------+----------------+-----------+-----------+---------------------+----------------+----------------+---------------------+------+----------+------------+----------------------+----------------------+--------------------+ | testdb | test_event_02 | root@localhost | SYSTEM | ONE TIME | 2017-08-03 04:24:48 | NULL | NULL | NULL | NULL | DISABLED | 0 | utf8 | utf8_general_ci | utf8_general_ci | | testdb | test_event_04 | root@localhost | SYSTEM | RECURRING | NULL | 2 | MINUTE | 2017-08-03 04:44:47 | NULL | DISABLED | 0 | utf8 | utf8_general_ci | utf8_general_ci | +--------+---------------+----------------+-----------+-----------+---------------------+----------------+----------------+---------------------+------+----------+------------+----------------------+----------------------+--------------------+ 2 rows in set
我们可以在ALTER EVENT语句之后使用ENABLE关键字来启用事件：
ALTER EVENT test_event_04 ENABLE;
查看下事件状态：
mysql> SHOW EVENTS FROM testdb; +--------+---------------+----------------+-----------+-----------+---------------------+----------------+----------------+---------------------+------+----------+------------+----------------------+----------------------+--------------------+ | Db | Name | Definer | Time zone | Type | Execute at | Interval value | Interval field | Starts | Ends | Status | Originator | character_set_client | collation_connection | Database Collation | +--------+---------------+----------------+-----------+-----------+---------------------+----------------+----------------+---------------------+------+----------+------------+----------------------+----------------------+--------------------+ | testdb | test_event_02 | root@localhost | SYSTEM | ONE TIME | 2017-08-03 04:24:48 | NULL | NULL | NULL | NULL | DISABLED | 0 | utf8 | utf8_general_ci | utf8_general_ci | | testdb | test_event_04 | root@localhost | SYSTEM | RECURRING | NULL | 2 | MINUTE | 2017-08-03 04:44:47 | NULL | ENABLED | 0 | utf8 | utf8_general_ci | utf8_general_ci | +--------+---------------+----------------+-----------+-----------+---------------------+----------------+----------------+---------------------+------+----------+------------+----------------------+----------------------+--------------------+ 2 rows in set
我们再来尝试使用ALTER EVENT重命名现有事件：
ALTER EVENT test_event_04 RENAME TO test_event_05;
来查看下事件状态：
mysql> SHOW EVENTS FROM testdb; +--------+---------------+----------------+-----------+-----------+---------------------+----------------+----------------+---------------------+------+----------+------------+----------------------+----------------------+--------------------+ | Db | Name | Definer | Time zone | Type | Execute at | Interval value | Interval field | Starts | Ends | Status | Originator | character_set_client | collation_connection | Database Collation | +--------+---------------+----------------+-----------+-----------+---------------------+----------------+----------------+---------------------+------+----------+------------+----------------------+----------------------+--------------------+ | testdb | test_event_02 | root@localhost | SYSTEM | ONE TIME | 2017-08-03 04:24:48 | NULL | NULL | NULL | NULL | DISABLED | 0 | utf8 | utf8_general_ci | utf8_general_ci | | testdb | test_event_05 | root@localhost | SYSTEM | RECURRING | NULL | 2 | MINUTE | 2017-08-03 04:44:47 | NULL | ENABLED | 0 | utf8 | utf8_general_ci | utf8_general_ci | +--------+---------------+----------------+-----------+-----------+---------------------+----------------+----------------+---------------------+------+----------+------------+----------------------+----------------------+--------------------+ 2 rows in set
完事再来通过使用RENAME TO子句将事件从一个数据库移动到另一个数据库中：
ALTER EVENT testdb.test_event_05 RENAME TO newdb.test_event_05;
再来查看事件状态：
mysql> SHOW EVENTS FROM newdb; +-------+---------------+----------------+-----------+-----------+------------+----------------+----------------+---------------------+------+---------+------------+----------------------+----------------------+--------------------+ | Db | Name | Definer | Time zone | Type | Execute at | Interval value | Interval field | Starts | Ends | Status | Originator | character_set_client | collation_connection | Database Collation | +-------+---------------+----------------+-----------+-----------+------------+----------------+----------------+---------------------+------+---------+------------+----------------------+----------------------+--------------------+ | newdb | test_event_05 | root@localhost | SYSTEM | RECURRING | NULL | 2 | MINUTE | 2017-08-03 04:44:47 | NULL | ENABLED | 0 | utf8 | utf8_general_ci | utf8_general_ci | +-------+---------------+----------------+-----------+-----------+------------+----------------+----------------+---------------------+------+---------+------------+----------------------+----------------------+--------------------+ 1 row in set
好啦，本次记录就到这里了。
更多关于MySQL相关内容感兴趣的读者可查看本站专题：《MySQL索引操作技巧汇总》、《MySQL常用函数大汇总》、《MySQL日志操作技巧大全》、《MySQL事务操作技巧汇总》、《MySQL存储过程技巧大全》及《MySQL数据库锁相关技巧汇总》
希望本文所述对大家MySQL数据库计有所帮助。
富贵资源网 Design By www.hznty.com
广告合作：本站广告合作请联系QQ：858582 申请时备注：广告合作（否则不回）
免责声明：本站资源来自互联网收集,仅供用于学习和交流,请遵循相关法律法规,本站一切资源不代表本站立场,如有侵权、后门、不妥请联系本站删除！
免责声明：本站资源来自互联网收集,仅供用于学习和交流,请遵循相关法律法规,本站一切资源不代表本站立场,如有侵权、后门、不妥请联系本站删除！
富贵资源网 Design By www.hznty.com
暂无评论...
P70系列延期，华为新旗舰将在下月发布
3月20日消息，近期博主@数码闲聊站 透露，原定三月份发布的华为新旗舰P70系列延期发布，预计4月份上市。
而博主@定焦数码 爆料，华为的P70系列在定位上已经超过了Mate60，成为了重要的旗舰系列之一。它肩负着重返影像领域顶尖的使命。那么这次P70会带来哪些令人惊艳的创新呢？
根据目前爆料的消息来看，华为P70系列将推出三个版本，其中P70和P70 Pro采用了三角形的摄像头模组设计，而P70 Art则采用了与上一代P60 Art相似的不规则形状设计。这样的外观是否好看见仁见智，但辨识度绝对拉满。