### 25.4.6 The Event Scheduler and MySQL Privileges

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 To enable or disable the execution of scheduled events, it is necessary to set the value of the global [`event_scheduler`](server-system-variables.html#sysvar_event_scheduler) system variable. This requires privileges sufficient to set global system variables. See [Section 5.1.9.1, “System Variable Privileges”](system-variable-privileges.html).

 The [`EVENT`](privileges-provided.html#priv_event) privilege governs the creation, modification, and deletion of events. This privilege can be bestowed using [`GRANT`](grant.html). For example, this [`GRANT`](grant.html) statement confers the [`EVENT`](privileges-provided.html#priv_event) privilege for the schema named `myschema` on the user `jon@ghidora`:

```
GRANT EVENT ON myschema.* TO jon@ghidora;
```

 (We assume that this user account already exists, and that we wish for it to remain unchanged otherwise.)

 To grant this same user the [`EVENT`](privileges-provided.html#priv_event) privilege on all schemas, use the following statement:

```
GRANT EVENT ON *.* TO jon@ghidora;
```

 The [`EVENT`](privileges-provided.html#priv_event) privilege has global or schema-level scope. Therefore, trying to grant it on a single table results in an error as shown:

```
mysql> GRANT EVENT ON myschema.mytable TO jon@ghidora;
ERROR 1144 (42000): Illegal GRANT/REVOKE command; please
consult the manual to see which privileges can be used
```

 It is important to understand that an event is executed with the privileges of its definer, and that it cannot perform any actions for which its definer does not have the requisite privileges. For example, suppose that `jon@ghidora` has the [`EVENT`](privileges-provided.html#priv_event) privilege for `myschema`. Suppose also that this user has the [`SELECT`](privileges-provided.html#priv_select) privilege for `myschema`, but no other privileges for this schema. It is possible for `jon@ghidora` to create a new event such as this one:

```
CREATE EVENT e_store_ts
    ON SCHEDULE
      EVERY 10 SECOND
    DO
      INSERT INTO myschema.mytable VALUES (UNIX_TIMESTAMP());
```

 The user waits for a minute or so, and then performs a `SELECT * FROM mytable;` query, expecting to see several new rows in the table. Instead, the table is empty. Since the user does not have the [`INSERT`](privileges-provided.html#priv_insert) privilege for the table in question, the event has no effect.

 If you inspect the MySQL error log (`*`hostname`*.err`), you can see that the event is executing, but the action it is attempting to perform fails:

```
2013-09-24T12:41:31.261992Z 25 [ERROR] Event Scheduler:
[jon@ghidora][cookbook.e_store_ts] INSERT command denied to user
'jon'@'ghidora' for table 'mytable'
2013-09-24T12:41:31.262022Z 25 [Note] Event Scheduler:
[jon@ghidora].[myschema.e_store_ts] event execution failed.
2013-09-24T12:41:41.271796Z 26 [ERROR] Event Scheduler:
[jon@ghidora][cookbook.e_store_ts] INSERT command denied to user
'jon'@'ghidora' for table 'mytable'
2013-09-24T12:41:41.272761Z 26 [Note] Event Scheduler:
[jon@ghidora].[myschema.e_store_ts] event execution failed.
```

 Since this user very likely does not have access to the error log, it is possible to verify whether the event's action statement is valid by executing it directly:

```
mysql> INSERT INTO myschema.mytable VALUES (UNIX_TIMESTAMP());
ERROR 1142 (42000): INSERT command denied to user
'jon'@'ghidora' for table 'mytable'
```

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 Inspection of the [`INFORMATION_SCHEMA.EVENTS`](information-schema-events-table.html) table shows that `e_store_ts` exists and is enabled, but its `LAST_EXECUTED` column is `NULL`:

```
mysql> SELECT * FROM INFORMATION_SCHEMA.EVENTS
     >     WHERE EVENT_NAME='e_store_ts'
     >     AND EVENT_SCHEMA='myschema'\G
*************************** 1. row ***************************
   EVENT_CATALOG: NULL
    EVENT_SCHEMA: myschema
      EVENT_NAME: e_store_ts
         DEFINER: jon@ghidora
      EVENT_BODY: SQL
EVENT_DEFINITION: INSERT INTO myschema.mytable VALUES (UNIX_TIMESTAMP())
      EVENT_TYPE: RECURRING
      EXECUTE_AT: NULL
  INTERVAL_VALUE: 5
  INTERVAL_FIELD: SECOND
        SQL_MODE: NULL
          STARTS: 0000-00-00 00:00:00
            ENDS: 0000-00-00 00:00:00
          STATUS: ENABLED
   ON_COMPLETION: NOT PRESERVE
         CREATED: 2006-02-09 22:36:06
    LAST_ALTERED: 2006-02-09 22:36:06
   LAST_EXECUTED: NULL
   EVENT_COMMENT:
1 row in set (0.00 sec)
```

 To rescind the [`EVENT`](privileges-provided.html#priv_event) privilege, use the [`REVOKE`](revoke.html) statement. In this example, the [`EVENT`](privileges-provided.html#priv_event) privilege on the schema `myschema` is removed from the `jon@ghidora` user account:

```
REVOKE EVENT ON myschema.* FROM jon@ghidora;
```

Important

 Revoking the [`EVENT`](privileges-provided.html#priv_event) privilege from a user does not delete or disable any events that may have been created by that user.

 An event is not migrated or dropped as a result of renaming or dropping the user who created it.

 Suppose that the user `jon@ghidora` has been granted the [`EVENT`](privileges-provided.html#priv_event) and [`INSERT`](privileges-provided.html#priv_insert) privileges on the `myschema` schema. This user then creates the following event:

```
CREATE EVENT e_insert
    ON SCHEDULE
      EVERY 7 SECOND
    DO
      INSERT INTO myschema.mytable;
```

 After this event has been created, `root` revokes the [`EVENT`](privileges-provided.html#priv_event) privilege for `jon@ghidora`. However, `e_insert` continues to execute, inserting a new row into `mytable` each seven seconds. The same would be true if `root` had issued either of these statements:

* `DROP USER jon@ghidora;`

* `RENAME USER jon@ghidora TO someotherguy@ghidora;`

 You can verify that this is true by examining the [`INFORMATION_SCHEMA.EVENTS`](information-schema-events-table.html) table (see [Section 26.3.14, “The INFORMATION\_SCHEMA EVENTS Table”](information-schema-events-table.html)) before and after issuing a [`DROP USER`](drop-user.html) or [`RENAME USER`](rename-user.html) statement.

 Event definitions are stored in the data dictionary. To drop an event created by another user account, you must be the MySQL `root` user or another user with the necessary privileges.

 Users' [`EVENT`](privileges-provided.html#priv_event) privileges are stored in the `Event_priv` columns of the `mysql.user` and `mysql.db` tables. In both cases, this column holds one of the values '`Y`' or '`N`'. '`N`' is the default. `mysql.user.Event_priv` is set to '`Y`' for a given user only if that user has the global [`EVENT`](privileges-provided.html#priv_event) privilege (that is, if the privilege was bestowed using `GRANT EVENT ON *.*`). For a schema-level [`EVENT`](privileges-provided.html#priv_event) privilege, [`GRANT`](grant.html) creates a row in `mysql.db` and sets that row's `Db` column to the name of the schema, the `User` column to the name of the user, and the `Event_priv` column to '`Y`'. There should never be any need to manipulate these tables directly, since the [`GRANT EVENT`](grant.html) and `REVOKE EVENT` statements perform the required operations on them.

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 Five status variables provide counts of event-related operations (but *not* of statements executed by events; see [Section 25.8, “Restrictions on Stored Programs”](stored-program-restrictions.html)). These are:

* `Com_create_event`: The number of [`CREATE EVENT`](create-event.html) statements executed since the last server restart.

* `Com_alter_event`: The number of [`ALTER EVENT`](alter-event.html) statements executed since the last server restart.

* `Com_drop_event`: The number of [`DROP EVENT`](drop-event.html) statements executed since the last server restart.

* `Com_show_create_event`: The number of [`SHOW CREATE EVENT`](show-create-event.html) statements executed since the last server restart.

* `Com_show_events`: The number of [`SHOW EVENTS`](show-events.html) statements executed since the last server restart.

 You can view current values for all of these at one time by running the statement `SHOW STATUS LIKE '%event%';`.

