<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <HTML ><HEAD ><TITLE >CREATE CONSTRAINT TRIGGER</TITLE ><META NAME="GENERATOR" CONTENT="Modular DocBook HTML Stylesheet Version 1.79"><LINK REV="MADE" HREF="mailto:pgsql-docs@postgresql.org"><LINK REL="HOME" TITLE="PostgreSQL 9.0.19 Documentation" HREF="index.html"><LINK REL="UP" TITLE="SQL Commands" HREF="sql-commands.html"><LINK REL="PREVIOUS" TITLE="CREATE CAST" HREF="sql-createcast.html"><LINK REL="NEXT" TITLE="CREATE CONVERSION" HREF="sql-createconversion.html"><LINK REL="STYLESHEET" TYPE="text/css" HREF="stylesheet.css"><META HTTP-EQUIV="Content-Type" CONTENT="text/html; charset=ISO-8859-1"><META NAME="creation" CONTENT="2015-02-07T09:43:28"></HEAD ><BODY CLASS="REFENTRY" ><DIV CLASS="NAVHEADER" ><TABLE SUMMARY="Header navigation table" WIDTH="100%" BORDER="0" CELLPADDING="0" CELLSPACING="0" ><TR ><TH COLSPAN="5" ALIGN="center" VALIGN="bottom" ><A HREF="index.html" >PostgreSQL 9.0.19 Documentation</A ></TH ></TR ><TR ><TD WIDTH="10%" ALIGN="left" VALIGN="top" ><A TITLE="CREATE CAST" HREF="sql-createcast.html" ACCESSKEY="P" >Prev</A ></TD ><TD WIDTH="10%" ALIGN="left" VALIGN="top" ><A HREF="sql-commands.html" ACCESSKEY="U" >Up</A ></TD ><TD WIDTH="60%" ALIGN="center" VALIGN="bottom" ></TD ><TD WIDTH="20%" ALIGN="right" VALIGN="top" ><A TITLE="CREATE CONVERSION" HREF="sql-createconversion.html" ACCESSKEY="N" >Next</A ></TD ></TR ></TABLE ><HR ALIGN="LEFT" WIDTH="100%"></DIV ><H1 ><A NAME="SQL-CREATECONSTRAINT" ></A >CREATE CONSTRAINT TRIGGER</H1 ><DIV CLASS="REFNAMEDIV" ><A NAME="AEN59748" ></A ><H2 >Name</H2 >CREATE CONSTRAINT TRIGGER -- define a new constraint trigger</DIV ><DIV CLASS="REFSYNOPSISDIV" ><A NAME="AEN59753" ></A ><H2 >Synopsis</H2 ><PRE CLASS="SYNOPSIS" >CREATE CONSTRAINT TRIGGER <TT CLASS="REPLACEABLE" ><I >name</I ></TT > AFTER <TT CLASS="REPLACEABLE" ><I >event</I ></TT > [ OR ... ] ON <TT CLASS="REPLACEABLE" ><I >table_name</I ></TT > [ FROM <TT CLASS="REPLACEABLE" ><I >referenced_table_name</I ></TT > ] { NOT DEFERRABLE | [ DEFERRABLE ] { INITIALLY IMMEDIATE | INITIALLY DEFERRED } } FOR EACH ROW [ WHEN ( <TT CLASS="REPLACEABLE" ><I >condition</I ></TT > ) ] EXECUTE PROCEDURE <TT CLASS="REPLACEABLE" ><I >function_name</I ></TT > ( <TT CLASS="REPLACEABLE" ><I >arguments</I ></TT > )</PRE ></DIV ><DIV CLASS="REFSECT1" ><A NAME="AEN59762" ></A ><H2 >Description</H2 ><P > <TT CLASS="COMMAND" >CREATE CONSTRAINT TRIGGER</TT > creates a <I CLASS="FIRSTTERM" >constraint trigger</I >. This is the same as a regular trigger except that the timing of the trigger firing can be adjusted using <A HREF="sql-set-constraints.html" >SET CONSTRAINTS</A >. Constraint triggers must be <TT CLASS="LITERAL" >AFTER ROW</TT > triggers. They can be fired either at the end of the statement causing the triggering event, or at the end of the containing transaction; in the latter case they are said to be <I CLASS="FIRSTTERM" >deferred</I >. A pending deferred-trigger firing can also be forced to happen immediately by using <TT CLASS="COMMAND" >SET CONSTRAINTS</TT >. </P ></DIV ><DIV CLASS="REFSECT1" ><A NAME="AEN59771" ></A ><H2 >Parameters</H2 ><P ></P ><DIV CLASS="VARIABLELIST" ><DL ><DT ><TT CLASS="REPLACEABLE" ><I >name</I ></TT ></DT ><DD ><P > The name of the constraint trigger. This is also the name to use when modifying the trigger's behavior using <TT CLASS="COMMAND" >SET CONSTRAINTS</TT >. The name cannot be schema-qualified — the trigger inherits the schema of its table. </P ></DD ><DT ><TT CLASS="REPLACEABLE" ><I >event</I ></TT ></DT ><DD ><P > One of <TT CLASS="LITERAL" >INSERT</TT >, <TT CLASS="LITERAL" >UPDATE</TT >, or <TT CLASS="LITERAL" >DELETE</TT >; this specifies the event that will fire the trigger. Multiple events can be specified using <TT CLASS="LITERAL" >OR</TT >. </P ></DD ><DT ><TT CLASS="REPLACEABLE" ><I >table_name</I ></TT ></DT ><DD ><P > The (possibly schema-qualified) name of the table in which the triggering events occur. </P ></DD ><DT ><TT CLASS="REPLACEABLE" ><I >referenced_table_name</I ></TT ></DT ><DD ><P > The (possibly schema-qualified) name of another table referenced by the constraint. This option is used for foreign-key constraints and is not recommended for general use. </P ></DD ><DT ><TT CLASS="LITERAL" >DEFERRABLE</TT ><BR><TT CLASS="LITERAL" >NOT DEFERRABLE</TT ><BR><TT CLASS="LITERAL" >INITIALLY IMMEDIATE</TT ><BR><TT CLASS="LITERAL" >INITIALLY DEFERRED</TT ></DT ><DD ><P > The default timing of the trigger. See the <A HREF="sql-createtable.html" >CREATE TABLE</A > documentation for details of these constraint options. </P ></DD ><DT ><TT CLASS="REPLACEABLE" ><I >condition</I ></TT ></DT ><DD ><P > A Boolean expression that determines whether the trigger function will actually be executed. This acts the same as in <A HREF="sql-createtrigger.html" >CREATE TRIGGER</A >. Note in particular that evaluation of the <TT CLASS="LITERAL" >WHEN</TT > condition is not deferred, but occurs immediately after the row update operation is performed. If the condition does not evaluate to <TT CLASS="LITERAL" >true</TT > then the trigger is not queued for deferred execution. </P ></DD ><DT ><TT CLASS="REPLACEABLE" ><I >function_name</I ></TT ></DT ><DD ><P > The function to call when the trigger is fired. See <A HREF="sql-createtrigger.html" >CREATE TRIGGER</A > for details. </P ></DD ><DT ><TT CLASS="REPLACEABLE" ><I >arguments</I ></TT ></DT ><DD ><P > Optional argument strings to pass to the trigger function. See <A HREF="sql-createtrigger.html" >CREATE TRIGGER</A > for details. </P ></DD ></DL ></DIV ></DIV ><DIV CLASS="REFSECT1" ><A NAME="AEN59831" ></A ><H2 >Compatibility</H2 ><P > <TT CLASS="COMMAND" >CREATE CONSTRAINT TRIGGER</TT > is a <SPAN CLASS="PRODUCTNAME" >PostgreSQL</SPAN > extension of the <ACRONYM CLASS="ACRONYM" >SQL</ACRONYM > standard. </P ></DIV ><DIV CLASS="REFSECT1" ><A NAME="AEN59837" ></A ><H2 >See Also</H2 ><A HREF="sql-createtrigger.html" >CREATE TRIGGER</A >, <A HREF="sql-droptrigger.html" >DROP TRIGGER</A >, <A HREF="sql-set-constraints.html" >SET CONSTRAINTS</A ></DIV ><DIV CLASS="NAVFOOTER" ><HR ALIGN="LEFT" WIDTH="100%"><TABLE SUMMARY="Footer navigation table" WIDTH="100%" BORDER="0" CELLPADDING="0" CELLSPACING="0" ><TR ><TD WIDTH="33%" ALIGN="left" VALIGN="top" ><A HREF="sql-createcast.html" ACCESSKEY="P" >Prev</A ></TD ><TD WIDTH="34%" ALIGN="center" VALIGN="top" ><A HREF="index.html" ACCESSKEY="H" >Home</A ></TD ><TD WIDTH="33%" ALIGN="right" VALIGN="top" ><A HREF="sql-createconversion.html" ACCESSKEY="N" >Next</A ></TD ></TR ><TR ><TD WIDTH="33%" ALIGN="left" VALIGN="top" >CREATE CAST</TD ><TD WIDTH="34%" ALIGN="center" VALIGN="top" ><A HREF="sql-commands.html" ACCESSKEY="U" >Up</A ></TD ><TD WIDTH="33%" ALIGN="right" VALIGN="top" >CREATE CONVERSION</TD ></TR ></TABLE ></DIV ></BODY ></HTML >