MySQL 如何修改现有的MySQL事件？

通过ALTER EVENT语句的帮助，我们可以修改现有的MySQL事件。我们可以更改事件的各种属性。ALTER EVENT有以下语法 −

ALTER EVENT event_name
    ON SCHEDULE schedule
ON COMPLETION [NOT] PRESERVE
    RENAME TO new_event_name
    ENABLE | DISABLE
             DO
        event_body

为了理解，我们以下面的示例进行说明 −

阅读更多：MySQL 教程

示例

假设我们有如下事件 −

mysql> Create event hello ON SCHEDULE EVERY 1 Minute DO INSERT INTO event_messages(message, generated_at) Values ('Alter event testing', NOW());
Query OK, 0 rows affected (0.00 sec)

mysql> select * from event_messages;
+----+---------------------+---------------------+
| ID | MESSAGE             | Generated_at        |
+----+---------------------+---------------------+
|  1 | Without Preserve    | 2017-11-22 20:32:13 |
|  2 | With Preserve       | 2017-11-22 20:35:12 |
|  3 | Alter event testing | 2017-11-22 21:08:37 |
+----+---------------------+---------------------+
3 rows in set (0.00 sec)

mysql> ALTER EVENT hello ON SCHEDULE EVERY 2 MINUTE;
Query OK, 0 rows affected (0.00 sec)

上述查询将从1分钟改为2分钟修改事件的计划。下面的查询将更改事件的内容。

mysql> ALTER EVENT hello DO INSERT INTO event_messages(message,generated_at) VALUES('ALTERED',NOW());
Query OK, 0 rows affected (0.00 sec)

mysql> select * from event_messages;
+----+---------------------+---------------------+
| ID | MESSAGE             | Generated_at        |
+----+---------------------+---------------------+
|  1 | Without Preserve    | 2017-11-22 20:32:13 |
|  2 | With Preserve       | 2017-11-22 20:35:12 |
|  3 | Alter event testing | 2017-11-22 21:08:37 |
|  4 | Alter event testing | 2017-11-22 21:09:15 |
|  5 | ALTERED             | 2017-11-22 21:11:15 |
+----+---------------------+---------------------+
5 rows in set (0.00 sec)