mysql事件之修改事件（ALTER EVENT）、禁用事件（DISABLE）、啟用事件（ENABLE）、事件重命名及數(shù)據(jù)庫事件遷移操作詳解

更新時間：2019年12月18日 09:29:39 作者：luyaran

這篇文章主要介紹了mysql事件之修改事件（ALTER EVENT）、禁用事件（DISABLE）、啟用事件（ENABLE）、事件重命名及數(shù)據(jù)庫事件遷移操作,詳細(xì)分析了mysql數(shù)據(jù)庫事件的修改、禁用、啟用、重命名、遷移等原理與操作技巧,需要的朋友可以參考下

本文實例講述了mysql事件之修改事件（ALTER EVENT）、禁用事件（DISABLE）、啟用事件（ENABLE）、事件重命名及數(shù)據(jù)庫事件遷移操作。分享給大家供大家參考，具體如下：

我們要知道，MySQL允許我們更改現(xiàn)有事件的各種屬性。如果我們要更改現(xiàn)有事件，可以使用ALTER EVENT語句，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語句僅適用于存在的事件，如果我們嘗試修改不存在的事件，MySQL將會發(fā)出一條錯誤消息，因此在更改事件之前，應(yīng)先使用SHOW EVENTS語句檢查事件的存在：

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

創(chuàng)建一個每分鐘將一條新記錄插入到messages表中的示例事件來演示如何使用ALTER EVENT語句的各種功能：

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());

我們來把事件修改為為每2分鐘運行一次：

ALTER EVENT test_event_04
ON SCHEDULE EVERY 2 MINUTE;

我們還可以通過指定新的邏輯來更改事件的主體代碼：

ALTER EVENT test_event_04
DO
  INSERT INTO messages(message,created_at)
  VALUES('Message from event',NOW());
-- 清空表中的數(shù)據(jù)
truncate messages;

修改完成后，可以等待2分鐘，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

我們可以在ALTER EVENT語句之后使用DISABLE關(guān)鍵字來禁用某個事件：

ALTER EVENT test_event_04
DISABLE;

我們也可以通過使用SHOW EVENTS語句來查看事件的狀態(tài)：

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

我們可以在ALTER EVENT語句之后使用ENABLE關(guān)鍵字來啟用事件：

ALTER EVENT test_event_04
ENABLE;

查看下事件狀態(tài)：

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

我們再來嘗試使用ALTER EVENT重命名現(xiàn)有事件：

ALTER EVENT test_event_04
RENAME TO test_event_05;

來查看下事件狀態(tài)：

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

完事再來通過使用RENAME TO子句將事件從一個數(shù)據(jù)庫移動到另一個數(shù)據(jù)庫中：

ALTER EVENT testdb.test_event_05
RENAME TO newdb.test_event_05;

再來查看事件狀態(tài)：

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，本次記錄就到這里了。

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