The ALTER EVENT statement in MySQL is used to modify the properties of an existing event. An event in MySQL is a scheduled task that can be executed at a specified time or interval. The ALTER EVENT statement allows you to change various attributes of an event without having to drop and recreate it.
Syntax
Here is the basic syntax of the ALTER EVENT statement:
ALTER EVENT [IF EXISTS] event_name ON SCHEDULE schedule [ON COMPLETION [NOT] PRESERVE] [RENAME TO new_event_name] [ENABLE | DISABLE] [COMMENT 'comment'] [DO sql_statement];
Let’s go through the various components of this statement:
IF EXISTS: This optional clause allows you to check if the event exists before attempting to alter it. If the event doesn’t exist, the statement will not produce an error.
event_name: Specifies the name of the event that you want to alter.
ON SCHEDULE schedule: Specifies the new schedule for the event. The schedule can include options such as EVERY to specify the frequency, STARTS to set the start time, and ENDS to set the end time.
ON COMPLETION [NOT] PRESERVE: This clause determines whether the event’s status should be preserved or not after it completes. If PRESERVE is specified, the event status is preserved; otherwise, it is not.
RENAME TO new_event_name: Allows you to change the name of the event.
ENABLE | DISABLE: Specifies whether the event should be enabled or disabled. A disabled event will not be executed until it is enabled again.
COMMENT ‘comment’: This is an optional clause that allows you to add or modify a comment associated with the event.
DO sql_statement: Specifies the SQL statement that the event should execute. This can be modified using the ALTER EVENT statement.
Example
Here is a simple example of using ALTER EVENT to modify the schedule of an existing event:
ALTER EVENT my_event ON SCHEDULE EVERY 1 DAY STARTS '2024-01-07 12:00:00';
In this example, the event named my_event will be altered to run every day starting from January 7, 2024, at 12:00:00.
It’s important to note that the user executing the ALTER EVENT statement must have the EVENT privilege, and the event must already exist for modification.
The ALTER EVENT statement is a versatile tool for modifying MySQL events. It allows you to make changes to the schedule, action, and other properties of an event without having to drop and recreate it. This can save you time and effort when managing your scheduled tasks.