ALTER EVENT - MySQL

Overview

The ALTER EVENT command in MySQL modifies the behavior and properties of an existing event. It allows you to change the event’s schedule, definition, and other attributes.

Syntax

ALTER EVENT event_name
ON SCHEDULE schedule
AS statement
[WITH [old | new] [retention period]]
[COMMENT 'comment']
[LOCK | NO LOCK]
[DISABLE | ENABLE]

Options/Flags

| Option/Flag | Description | Default |
|—|—|—|
| ON SCHEDULE | Modifies the event’s schedule. | – |
| AS statement | Alters the event’s definition (body). | – |
| WITH OLD | Preserves the old event data in temporary tables. | No |
| WITH NEW | Preserves the new event data in temporary tables. | No |
| retention period | Specifies the retention period for temporary tables. | 0 (no retention) |
| COMMENT | Adds or modifies a comment for the event. | No |
| LOCK | Acquires a lock on the event before modifying it. | No |
| NO LOCK | Modifies the event without acquiring a lock. | Yes |
| DISABLE | Deactivates the event, preventing it from executing. | No |
| ENABLE | Activates the event, allowing it to execute as scheduled. | No |

Examples

Changing the event’s schedule:

ALTER EVENT my_event ON SCHEDULE
EVERY 1 DAY
AT '02:00:00'

Modifying the event’s definition:

ALTER EVENT my_event AS
INSERT INTO table1 (col1, col2)
VALUES (1, 'value1');

Preserving old event data:

ALTER EVENT my_event WITH OLD
AS
SELECT * FROM table1 WHERE modified = 1;

Adding a comment to the event:

ALTER EVENT my_event COMMENT 'This event triggers daily cleanup';

Common Issues

  • Event not found: The specified event may not exist. Vérify the event name.
  • Invalid schedule: The specified schedule may not be valid. Refer to the MySQL documentation for valid schedule formats.
  • Locked event: The event may be locked by another session. Retry the operation or use the LOCK option to acquire the lock explicitly.

Integration

The ALTER EVENT command can be combined with other MySQL commands for advanced event management. For instance, you can use the SHOW EVENTS command to view existing events, or use the CALL command to execute an event manually.

  • CREATE EVENT
  • DROP EVENT
  • SHOW EVENTS