CREATE EVENT

Schedule a new event for automatic execution. This statement defines a scheduled task that runs SQL commands at specific times or intervals.

Syntax

CREATE [OR REPLACE]
    [DEFINER = { user | CURRENT_USER | role | CURRENT_ROLE }]
    EVENT 
    [IF NOT EXISTS]
    event_name    
    ON SCHEDULE schedule
    [ON COMPLETION [NOT] PRESERVE]
    [ENABLE | DISABLE | DISABLE ON SLAVE]
    [COMMENT 'comment']
    DO sql_statement;

schedule:
    AT timestamp [+ INTERVAL interval] ...
  | EVERY interval 
    [STARTS timestamp [+ INTERVAL interval] ...] 
    [ENDS timestamp [+ INTERVAL interval] ...]

interval:
    quantity {YEAR | QUARTER | MONTH | DAY | HOUR | MINUTE |
              WEEK | SECOND | YEAR_MONTH | DAY_HOUR | DAY_MINUTE |
              DAY_SECOND | HOUR_MINUTE | HOUR_SECOND | MINUTE_SECOND}

Description

This statement creates and schedules a new event. It requires the EVENT privilege for the schema in which the event is to be created.

The minimum requirements for a valid CREATE EVENT statement are as follows:

• The keywords CREATE EVENT plus an event name, which uniquely identifies the event in the current schema.

• An ON SCHEDULE clause, which determines when and how often the event executes.

• A DO clause, which contains the SQL statement to be executed by an event.

Here is an example of a minimal CREATE EVENT statement:

CREATE EVENT myevent
    ON SCHEDULE AT CURRENT_TIMESTAMP + INTERVAL 1 HOUR
    DO
      UPDATE myschema.mytable SET mycol = mycol + 1;

The previous statement creates an event named myevent. This event executes once — one hour following its creation — by running an SQL statement that increments the value of the myschema.mytable table's mycol column by 1.

The event_name must be a valid MariaDB identifier with a maximum length of 64 characters. It may be delimited using back ticks, and may be qualified with the name of a database schema. An event is associated with both a MariaDB user (the definer) and a schema, and its name must be unique among names of events within that schema. In general, the rules governing event names are the same as those for names of stored routines. See Identifier Names.

If no schema is indicated as part of event_name, the default (current) schema is assumed.

For valid identifiers to use as event names, see Identifier Names.

OR REPLACE

Current

The OR REPLACE clause works like this: If the event already exists, instead of an error being returned, the existing event will be dropped and replaced by the newly defined event.

< 10.1.4

IF NOT EXISTS

If the IF NOT EXISTS clause is used, MariaDB will return a warning instead of an error if the event already exists. Cannot be used together with OR REPLACE.

ON SCHEDULE

The ON SCHEDULE clause can be used to specify when the event must be triggered.

AT

If you want to execute the event only once (one time event), you can use the AT keyword, followed by a timestamp. If you use CURRENT_TIMESTAMP, the event acts as soon as it is created. As a convenience, you can add one or more intervals to that timestamp. You can also specify a timestamp in the past, so that the event is stored but not triggered, until you modify it via ALTER EVENT.

The following example shows how to create an event that will be triggered tomorrow at a certain time:

CREATE EVENT example
ON SCHEDULE AT CURRENT_TIMESTAMP + INTERVAL 1 DAY + INTERVAL 3 HOUR
DO something;

You can also specify that an event must be triggered at a regular interval (recurring event). In such cases, use the EVERY clause followed by the interval.

If an event is recurring, you can specify when the first execution must happen via the STARTS clause and a maximum time for the last execution via the ENDS clause. STARTS and ENDS clauses are followed by a timestamp and, optionally, one or more intervals. The ENDS clause can specify a timestamp in the past, so that the event is stored but not executed until you modify it via ALTER EVENT.

In the following example, next month a recurring event will be triggered hourly for a week:

CREATE EVENT example
ON SCHEDULE EVERY 1 HOUR
STARTS CURRENT_TIMESTAMP + INTERVAL 1 MONTH
ENDS CURRENT_TIMESTAMP + INTERVAL 1 MONTH + INTERVAL 1 WEEK
DO some_task;

Intervals consist of a quantity and a time unit. The time units are the same used for other statements and time functions, except that you can't use microseconds for events. For simple time units, like HOUR or MINUTE, the quantity is an integer number, for example '10 MINUTE'. For composite time units, like HOUR_MINUTE or HOUR_SECOND, the quantity must be a string with all involved simple values and their separators, for example '2:30' or '2:30:30'.

ON COMPLETION [NOT] PRESERVE

The ON COMPLETION clause can be used to specify if the event must be deleted after its last execution (that is, after its AT or ENDS timestamp is past). By default, events are dropped when they are expired. To explicitly state that this is the desired behaviour, you can use ON COMPLETION NOT PRESERVE. Instead, if you want the event to be preserved, you can use ON COMPLETION PRESERVE.

In you specify ON COMPLETION NOT PRESERVE, and you specify a timestamp in the past for AT or ENDS clause, the event will be immediately dropped. In such cases, you will get a Note 1558: "Event execution time is in the past and ON COMPLETION NOT PRESERVE is set. The event was dropped immediately after creation".

ENABLE/DISABLE/DISABLE ON SLAVE

Events are ENABLEd by default. If you want to stop MariaDB from executing an event, you may specify DISABLE. When it is ready to be activated, you may enable it using ALTER EVENT. Another option is DISABLE ON SLAVE, which indicates that an event was created on a master and has been replicated to the slave, which is prevented from executing the event. If DISABLE ON SLAVE is specifically set, the event will be disabled everywhere. It will not be executed on the master or the replicas.

COMMENT

The COMMENT clause may be used to set a comment for the event. Maximum length for comments is 64 characters. The comment is a string, so it must be quoted. To see events comments, you can query the INFORMATION_SCHEMA.EVENTS table (the column is named EVENT_COMMENT).

Examples

Minimal CREATE EVENT statement:

CREATE EVENT myevent
    ON SCHEDULE AT CURRENT_TIMESTAMP + INTERVAL 1 HOUR
    DO
      UPDATE myschema.mytable SET mycol = mycol + 1;

An event that will be triggered tomorrow at a certain time:

CREATE EVENT example
ON SCHEDULE AT CURRENT_TIMESTAMP + INTERVAL 1 DAY + INTERVAL 3 HOUR
DO something;

Next month a recurring event will be triggered hourly for a week:

CREATE EVENT example
ON SCHEDULE EVERY 1 HOUR
STARTS CURRENT_TIMESTAMP + INTERVAL 1 MONTH
ENDS CURRENT_TIMESTAMP + INTERVAL 1 MONTH + INTERVAL 1 WEEK
DO some_task;

OR REPLACE and IF NOT EXISTS:

CREATE EVENT myevent
    ON SCHEDULE AT CURRENT_TIMESTAMP + INTERVAL 1 HOUR
    DO
      UPDATE myschema.mytable SET mycol = mycol + 1;
ERROR 1537 (HY000): Event 'myevent' already exists

CREATE OR REPLACE EVENT myevent
    ON SCHEDULE AT CURRENT_TIMESTAMP + INTERVAL 1 HOUR
    DO
      UPDATE myschema.mytable SET mycol = mycol + 1;;
Query OK, 0 rows affected (0.00 sec)

CREATE EVENT IF NOT EXISTS myevent
    ON SCHEDULE AT CURRENT_TIMESTAMP + INTERVAL 1 HOUR
    DO
      UPDATE myschema.mytable SET mycol = mycol + 1;
Query OK, 0 rows affected, 1 warning (0.00 sec)

 SHOW WARNINGS;
+-------+------+--------------------------------+
| Level | Code | Message                        |
+-------+------+--------------------------------+
| Note  | 1537 | Event 'myevent' already exists |
+-------+------+--------------------------------+

See Also

• Event Limitations

• Identifier Names

• Events Overview

• SHOW CREATE EVENT

• ALTER EVENT

• DROP EVENT

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