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 the
DEFINER
, ON SCHEDULE
,
ON COMPLETION
, COMMENT
,
ENABLE
/ DISABLE
, and
DO
clauses is exactly the same as
when used with CREATE EVENT
. (See
Section 13.1.12, “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 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 + 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.
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 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
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 both
ALTER EVENT
and
CREATE 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
to
yourevent
:
ALTER EVENT myevent
RENAME TO yourevent;
You can also move an event to a different database using
ALTER EVENT ... RENAME TO ...
and
notation, as shown here:
db_name.event_name
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.
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 source 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. See
Section 16.4.1.16, “Replication of Invoked Features”, for more
information.