ALTER
    [DEFINER = { user | CURRENT_USER }]
    EVENT event_name
    [ON SCHEDULE schedule]
    [ON COMPLETION [NOT] PRESERVE]
    [RENAME TO new_event_name]
    [ENABLE | DISABLE | DISABLE ON SLAVE]
    [COMMENT 'comment']
    [DO sql_statement]

The ALTER EVENT statement is used to change one or more of the characteristics of an existing event without the need to drop and recreate it. The syntax for each of the DEFINER, ON SCHEDULE, ON COMPLETION, COMMENT, ENABLE / DISABLE, and DO clauses is exactly the same as when used with CREATE EVENT. (See Section 25.2.2, “CREATE EVENT Syntax”.)

Support for the DEFINER clause was added in MySQL 5.1.17.

Beginning with MySQL 5.1.12, 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.

(In MySQL 5.1.11 and earlier, an event could be altered only by its definer, or by a user having the SUPER privilege.)

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 named myevent 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 for myevent 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 + 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 from mytable; it also changes the schedule for the event such that it executes once, one day after this ALTER EVENT statement is run.

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

It is necessary to include only those options in an ALTER EVENT statement which correspond to characteristics that you actually wish to change; options which are omitted retain their existing values. This includes any default values for CREATE EVENT such as ENABLE.

To disable myevent, use this ALTER 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 may not use stored routines or user-defined functions in such expressions, nor may you use any table references; however, you may use SELECT FROM DUAL. This is true for both ALTER EVENT and CREATE EVENT statements. Beginning with MySQL 5.1.13, references to stored routines, user-defined functions, and tables in such cases are specifically disallowed, and fail with an error (see Bug#22830).

An ALTER EVENT statement that contains another ALTER EVENT statement in its DO clause appears to succeed; however, 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 to yourevent:

ALTER EVENT myevent
    RENAME TO yourevent;

You can also move an event to a different database using ALTER EVENT ... RENAME TO ... and db_name.event_name 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 the olddb and newdb databases.

Beginning with MySQL 5.1.18, a third value may also appear in place of ENABLED or DISABLED; DISABLE ON SLAVE is used on a replication slave to indicate an event which was created on the master and replicated to the slave, but which is not executed on the slave. 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. See Section 19.3.1.5, “Replication of Invoked Features”, for more information.