---
title: "CREATE EVENT TRIGGER"
id: sql-createeventtrigger
pg_version: "20devel"
---

<a id="sql-createeventtrigger"></a>

# CREATE EVENT TRIGGER — define a new event trigger

## Synopsis

```
CREATE EVENT TRIGGER name
    ON event
    [ WHEN filter_variable IN (filter_value [, ... ]) [ AND ... ] ]
    EXECUTE { FUNCTION | PROCEDURE } function_name()
```

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## Description

`CREATE EVENT TRIGGER` creates a new event trigger. Whenever the designated event occurs and the `WHEN` condition associated with the trigger, if any, is satisfied, the trigger function will be executed. For a general introduction to event triggers, see [Chapter 38](event-triggers.md). The user who creates an event trigger becomes its owner. 

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## Parameters

**`name`**

 The name to give the new trigger. This name must be unique within the database. **`event`**

 The name of the event that triggers a call to the given function. See [Section 38.1](event-trigger-definition.md) for more information on event names. **`filter_variable`**

 The name of a variable used to filter events. This makes it possible to restrict the firing of the trigger to a subset of the cases in which it is supported. Currently the only supported `filter_variable` is `TAG`. **`filter_value`**

 A list of values for the associated `filter_variable` for which the trigger should fire. For `TAG`, this means a list of command tags (e.g., `'DROP FUNCTION'`). **`function_name`**

 A user-supplied function that is declared as taking no argument and returning type `event_trigger`.  In the syntax of `CREATE EVENT TRIGGER`, the keywords `FUNCTION` and `PROCEDURE` are equivalent, but the referenced function must in any case be a function, not a procedure. The use of the keyword `PROCEDURE` here is historical and deprecated. <a id="sql-createeventtrigger-notes"></a>

## Notes

Only superusers can create event triggers. 

Event triggers are disabled in single-user mode (see [postgres](app-postgres.md)) as well as when [`event_triggers` (`boolean`)](runtime-config-client.md#guc-event-triggers) is set to `false`. If an erroneous event trigger disables the database so much that you can't even drop the trigger, restart with [`event_triggers` (`boolean`)](runtime-config-client.md#guc-event-triggers) set to `false` to temporarily disable event triggers, or in single-user mode, and you'll be able to do that. 

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## Examples

Forbid the execution of any [DDL](ddl.md) command: 
CREATE OR REPLACE FUNCTION abort_any_command()
  RETURNS event_trigger
 LANGUAGE plpgsql
  AS $$
BEGIN
  RAISE EXCEPTION 'command % is disabled', tg_tag;
END;
$$;

CREATE EVENT TRIGGER abort_ddl ON ddl_command_start
   EXECUTE FUNCTION abort_any_command();


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## Compatibility

There is no `CREATE EVENT TRIGGER` statement in the SQL standard. 

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## See Also

[ALTER EVENT TRIGGER](sql-altereventtrigger.md), [DROP EVENT TRIGGER](sql-dropeventtrigger.md), [CREATE FUNCTION](sql-createfunction.md)