MySQL :: MySQL 8.0 Reference Manual :: 15.1.3 ALTER EVENT Statement (original) (raw)

15.1.3 ALTER EVENT Statement

ALTER
    [DEFINER = user]
    EVENT event_name
    [ON SCHEDULE schedule]
    [ON COMPLETION [NOT] PRESERVE]
    [RENAME TO new_event_name]
    [ENABLE | DISABLE | DISABLE ON SLAVE]
    [COMMENT 'string']
    [DO event_body]

The ALTER EVENT statement changes one or more of the characteristics of an existing event without the need to drop and recreate it. The syntax for each of theDEFINER, ON SCHEDULE,ON COMPLETION, COMMENT,ENABLE / DISABLE, andDO clauses is exactly the same as when used with CREATE EVENT. (SeeSection 15.1.13, “CREATE EVENT Statement”.)

Any user can alter an event defined on a database for which that user has the EVENT privilege. When a user executes a successful ALTER EVENT statement, that user becomes the definer for the affected event.

ALTER EVENT works only with an existing event:

mysql> ALTER EVENT no_such_event 
     >     ON SCHEDULE 
     >       EVERY '2:3' DAY_HOUR;
ERROR 1517 (HY000): Unknown event 'no_such_event'

In each of the following examples, assume that the event namedmyevent is defined as shown here:

CREATE EVENT myevent
    ON SCHEDULE
      EVERY 6 HOUR
    COMMENT 'A sample comment.'
    DO
      UPDATE myschema.mytable SET mycol = mycol + 1;

The following statement changes the schedule formyevent from once every six hours starting immediately to once every twelve hours, starting four hours from the time the statement is run:

ALTER EVENT myevent
    ON SCHEDULE
      EVERY 12 HOUR
    STARTS CURRENT_TIMESTAMP + INTERVAL 4 HOUR;

It is possible to change multiple characteristics of an event in a single statement. This example changes the SQL statement executed by myevent to one that deletes all records frommytable; it also changes the schedule for the event such that it executes once, one day after thisALTER EVENT statement is run.

ALTER EVENT myevent
    ON SCHEDULE
      AT CURRENT_TIMESTAMP + INTERVAL 1 DAY
    DO
      TRUNCATE TABLE myschema.mytable;

Specify the options in an ALTER EVENT statement only for those characteristics that you want to change; omitted options keep their existing values. This includes any default values for CREATE EVENT such as ENABLE.

To disable myevent, use thisALTER EVENT statement:

ALTER EVENT myevent
    DISABLE;

The ON SCHEDULE clause may use expressions involving built-in MySQL functions and user variables to obtain any of the timestamp or_interval_ values which it contains. You cannot use stored routines or loadable functions in such expressions, and you cannot use any table references; however, you can use SELECT FROM DUAL. This is true for bothALTER EVENT andCREATE EVENT statements. References to stored routines, loadable functions, and tables in such cases are specifically not permitted, and fail with an error (see Bug #22830).

Although an ALTER EVENT statement that contains another ALTER EVENT statement in its DO clause appears to succeed, when the server attempts to execute the resulting scheduled event, the execution fails with an error.

To rename an event, use the ALTER EVENT statement's RENAME TO clause. This statement renames the event myevent toyourevent:

ALTER EVENT myevent
    RENAME TO yourevent;

You can also move an event to a different database usingALTER EVENT ... RENAME TO ... and_`dbname.eventname`_ notation, as shown here:

ALTER EVENT olddb.myevent
    RENAME TO newdb.myevent;

To execute the previous statement, the user executing it must have the EVENT privilege on both theolddb and newdb databases.

Note

There is no RENAME EVENT statement.

The value DISABLE ON SLAVE is used on a replica instead of ENABLE or DISABLE to indicate an event that was created on the replication source server and replicated to the replica, but that is not executed on the replica. Normally, DISABLE ON SLAVE is set automatically as required; however, there are some circumstances under which you may want or need to change it manually. SeeSection 19.5.1.16, “Replication of Invoked Features”, for more information.