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Green_GoodERP18_FSJ_Standard/PostgreSQL/doc/postgresql/html/sql-createeventtrigger.html

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  1. <?xml version="1.0" encoding="UTF-8" standalone="no"?>

  2. <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>CREATE EVENT TRIGGER</title><link rel="stylesheet" type="text/css" href="stylesheet.css" /><link rev="made" href="pgsql-docs@lists.postgresql.org" /><meta name="generator" content="DocBook XSL Stylesheets V1.79.1" /><link rel="prev" href="sql-createdomain.html" title="CREATE DOMAIN" /><link rel="next" href="sql-createextension.html" title="CREATE EXTENSION" /></head><body><div xmlns="http://www.w3.org/TR/xhtml1/transitional" class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="5" align="center">CREATE EVENT TRIGGER</th></tr><tr><td width="10%" align="left"><a accesskey="p" href="sql-createdomain.html" title="CREATE DOMAIN">Prev</a> </td><td width="10%" align="left"><a accesskey="u" href="sql-commands.html" title="SQL Commands">Up</a></td><th width="60%" align="center">SQL Commands</th><td width="10%" align="right"><a accesskey="h" href="index.html" title="PostgreSQL 12.4 Documentation">Home</a></td><td width="10%" align="right"> <a accesskey="n" href="sql-createextension.html" title="CREATE EXTENSION">Next</a></td></tr></table><hr></hr></div><div class="refentry" id="SQL-CREATEEVENTTRIGGER"><div class="titlepage"></div><a id="id-1.9.3.63.1" class="indexterm"></a><div class="refnamediv"><h2><span class="refentrytitle">CREATE EVENT TRIGGER</span></h2><p>CREATE EVENT TRIGGER — define a new event trigger</p></div><div class="refsynopsisdiv"><h2>Synopsis</h2><pre class="synopsis">

  3. CREATE EVENT TRIGGER <em class="replaceable"><code>name</code></em>

  4.     ON <em class="replaceable"><code>event</code></em>

  5.     [ WHEN <em class="replaceable"><code>filter_variable</code></em> IN (filter_value [, ... ]) [ AND ... ] ]

  6.     EXECUTE { FUNCTION | PROCEDURE } <em class="replaceable"><code>function_name</code></em>()

  7. </pre></div><div class="refsect1" id="id-1.9.3.63.5"><h2>Description</h2><p>

  8.    <code class="command">CREATE EVENT TRIGGER</code> creates a new event trigger.

  9.    Whenever the designated event occurs and the <code class="literal">WHEN</code> condition

  10.    associated with the trigger, if any, is satisfied, the trigger function

  11.    will be executed.  For a general introduction to event triggers, see

  12.    <a class="xref" href="event-triggers.html" title="Chapter 39. Event Triggers">Chapter 39</a>.  The user who creates an event trigger

  13.    becomes its owner.

  14.   </p></div><div class="refsect1" id="id-1.9.3.63.6"><h2>Parameters</h2><div class="variablelist"><dl class="variablelist"><dt><span class="term"><em class="replaceable"><code>name</code></em></span></dt><dd><p>

  15.       The name to give the new trigger.  This name must be unique within

  16.       the database.

  17.      </p></dd><dt><span class="term"><em class="replaceable"><code>event</code></em></span></dt><dd><p>

  18.       The name of the event that triggers a call to the given function.

  19.       See <a class="xref" href="event-trigger-definition.html" title="39.1. Overview of Event Trigger Behavior">Section 39.1</a> for more information

  20.       on event names.

  21.      </p></dd><dt><span class="term"><em class="replaceable"><code>filter_variable</code></em></span></dt><dd><p>

  22.       The name of a variable used to filter events.  This makes it possible

  23.       to restrict the firing of the trigger to a subset of the cases in which

  24.       it is supported.  Currently the only supported

  25.       <em class="replaceable"><code>filter_variable</code></em>

  26.       is <code class="literal">TAG</code>.

  27.      </p></dd><dt><span class="term"><em class="replaceable"><code>filter_value</code></em></span></dt><dd><p>

  28.       A list of values for the

  29.       associated <em class="replaceable"><code>filter_variable</code></em>

  30.       for which the trigger should fire.  For <code class="literal">TAG</code>, this means a

  31.       list of command tags (e.g. <code class="literal">'DROP FUNCTION'</code>).

  32.      </p></dd><dt><span class="term"><em class="replaceable"><code>function_name</code></em></span></dt><dd><p>

  33.       A user-supplied function that is declared as taking no argument and

  34.       returning type <code class="literal">event_trigger</code>.

  35.      </p><p>

  36.       In the syntax of <code class="literal">CREATE EVENT TRIGGER</code>, the keywords

  37.       <code class="literal">FUNCTION</code> and <code class="literal">PROCEDURE</code> are

  38.       equivalent, but the referenced function must in any case be a function,

  39.       not a procedure.  The use of the keyword <code class="literal">PROCEDURE</code>

  40.       here is historical and deprecated.

  41.      </p></dd></dl></div></div><div class="refsect1" id="SQL-CREATEEVENTTRIGGER-NOTES"><h2>Notes</h2><p>

  42.    Only superusers can create event triggers.

  43.   </p><p>

  44.    Event triggers are disabled in single-user mode (see <a class="xref" href="app-postgres.html" title="postgres"><span class="refentrytitle"><span class="application">postgres</span></span></a>).  If an erroneous event trigger disables the

  45.    database so much that you can't even drop the trigger, restart in

  46.    single-user mode and you'll be able to do that.

  47.   </p></div><div class="refsect1" id="SQL-CREATEEVENTTRIGGER-EXAMPLES"><h2>Examples</h2><p>

  48.    Forbid the execution of any <a class="link" href="ddl.html" title="Chapter 5. Data Definition">DDL</a> command:

  49. 

  50. </p><pre class="programlisting">

  51. CREATE OR REPLACE FUNCTION abort_any_command()

  52.   RETURNS event_trigger

  53.  LANGUAGE plpgsql

  54.   AS $$

  55. BEGIN

  56.   RAISE EXCEPTION 'command % is disabled', tg_tag;

  57. END;

  58. $$;

  59. 

  60. CREATE EVENT TRIGGER abort_ddl ON ddl_command_start

  61.    EXECUTE FUNCTION abort_any_command();

  62. </pre></div><div class="refsect1" id="SQL-CREATEEVENTTRIGGER-COMPATIBILITY"><h2>Compatibility</h2><p>

  63.    There is no <code class="command">CREATE EVENT TRIGGER</code> statement in the

  64.    SQL standard.

  65.   </p></div><div class="refsect1" id="id-1.9.3.63.10"><h2>See Also</h2><span class="simplelist"><a class="xref" href="sql-altereventtrigger.html" title="ALTER EVENT TRIGGER"><span class="refentrytitle">ALTER EVENT TRIGGER</span></a>, <a class="xref" href="sql-dropeventtrigger.html" title="DROP EVENT TRIGGER"><span class="refentrytitle">DROP EVENT TRIGGER</span></a>, <a class="xref" href="sql-createfunction.html" title="CREATE FUNCTION"><span class="refentrytitle">CREATE FUNCTION</span></a></span></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="sql-createdomain.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="sql-commands.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="sql-createextension.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">CREATE DOMAIN </td><td width="20%" align="center"><a accesskey="h" href="index.html">Home</a></td><td width="40%" align="right" valign="top"> CREATE EXTENSION</td></tr></table></div></body></html>
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