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13.1.3 ALTER EVENT Syntax

Contents
  1. ALTER
  2.     [DEFINER = user]
  3.     EVENT event_name
  4.     [ON SCHEDULE schedule]
  5.     [ON COMPLETION [NOT] PRESERVE]
  6.     [RENAME TO new_event_name]
  7.     [ENABLE | DISABLE | DISABLE ON SLAVE]
  8.     [COMMENT 'string']
  9.     [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 the DEFINER, ON SCHEDULE, ON COMPLETION, COMMENT, ENABLE / DISABLE, and DO clauses is exactly the same as when used with CREATE EVENT. (See Section 13.1.13, “CREATE EVENT Syntax”.)

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:

  1. mysql> ALTER EVENT no_such_event
  2.      >     ON SCHEDULE
  3.      >       EVERY '2:3' DAY_HOUR;
  4. 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:

  1. CREATE EVENT myevent
  2.     ON SCHEDULE
  3.       EVERY 6 HOUR
  4.     COMMENT 'A sample comment.'
  5.     DO
  6.       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:

  1. ALTER EVENT myevent
  2.     ON SCHEDULE
  3.       EVERY 12 HOUR
  4.     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 from mytable; it also changes the schedule for the event such that it executes once, one day after this ALTER EVENT statement is run.

  1. ALTER EVENT myevent
  2.     ON SCHEDULE
  3.       AT CURRENT_TIMESTAMP + INTERVAL 1 DAY
  4.     DO
  5.       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 this ALTER EVENT statement:

  1. ALTER EVENT myevent
  2.     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 user-defined functions in such expressions, and you cannot use any table references; however, you can use SELECT FROM DUAL. This is true for both ALTER EVENT and CREATE EVENT statements. References to stored routines, user-defined 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 to yourevent:

  1. ALTER EVENT myevent
  2.     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:

  1. ALTER EVENT olddb.myevent
  2.     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.

Note

There is no RENAME EVENT statement.

The value DISABLE ON SLAVE is used on a replication slave instead of ENABLE or DISABLE to indicate an event that was created on the master and replicated to the slave, but that 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 17.4.1.16, “Replication of Invoked Features”, for more information.


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Document created the 26/06/2006, last modified the 26/10/2018
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