doc/src/sgml/ref/create_constraint.sgml

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   2 $PostgreSQL$
   3 PostgreSQL documentation
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   5
   6 <refentry id="SQL-CREATECONSTRAINT">
   7  <refmeta>
   8   <refentrytitle id="sql-createconstraint-title">CREATE CONSTRAINT TRIGGER</refentrytitle>
   9   <refmiscinfo>SQL - Language Statements</refmiscinfo>
  10  </refmeta>
  11
  12  <refnamediv>
  13   <refname>CREATE CONSTRAINT TRIGGER</refname>
  14   <refpurpose>define a new constraint trigger</refpurpose>
  15  </refnamediv>
  16
  17  <indexterm zone="sql-createconstraint">
  18   <primary>CREATE CONSTRAINT TRIGGER</primary>
  19  </indexterm>
  20
  21  <refsynopsisdiv>
  22 <synopsis>
  23 CREATE CONSTRAINT TRIGGER <replaceable class="parameter">name</replaceable>
  24     AFTER <replaceable class="parameter">event</replaceable> [ OR ... ]
  25     ON <replaceable class="parameter">table_name</replaceable>
  26     [ FROM <replaceable class="parameter">referenced_table_name</replaceable> ]
  27     { NOT DEFERRABLE | [ DEFERRABLE ] { INITIALLY IMMEDIATE | INITIALLY DEFERRED } }
  28     FOR EACH ROW
  29     EXECUTE PROCEDURE <replaceable class="parameter">funcname</replaceable> ( <replaceable class="parameter">arguments</replaceable> )
  30 </synopsis>
  31  </refsynopsisdiv>
  32
  33  <refsect1>
  34   <title>Description</title>
  35
  36   <para>
  37    <command>CREATE CONSTRAINT TRIGGER</command> creates a
  38    <firstterm>constraint trigger</>.  This is the same as a regular trigger
  39    except that the timing of the trigger firing can be adjusted using
  40    <xref linkend="SQL-SET-CONSTRAINTS" endterm="SQL-SET-CONSTRAINTS-TITLE">.
  41    Constraint triggers must be <literal>AFTER ROW</> triggers.  They can
  42    be fired either at the end of the statement causing the triggering event,
  43    or at the end of the containing transaction; in the latter case they are
  44    said to be <firstterm>deferred</>.  A pending deferred-trigger firing can
  45    also be forced to happen immediately by using <command>SET CONSTRAINTS</>.
  46   </para>
  47  </refsect1>
  48
  49  <refsect1>
  50   <title>Parameters</title>
  51
  52   <variablelist>
  53    <varlistentry>
  54     <term><replaceable class="PARAMETER">name</replaceable></term>
  55     <listitem>
  56      <para>
  57       The name of the constraint trigger.  This is also the name to use
  58       when modifying the trigger's behavior using <command>SET CONSTRAINTS</>.
  59       The name cannot be schema-qualified &mdash; the trigger inherits the
  60       schema of its table.
  61      </para>
  62     </listitem>
  63    </varlistentry>
  64
  65    <varlistentry>
  66     <term><replaceable class="PARAMETER">event</replaceable></term>
  67     <listitem>
  68      <para>
  69       One of <literal>INSERT</literal>, <literal>UPDATE</literal>, or
  70       <literal>DELETE</literal>; this specifies the event that will fire the
  71       trigger. Multiple events can be specified using <literal>OR</literal>.
  72      </para>
  73     </listitem>
  74    </varlistentry>
  75
  76    <varlistentry>
  77     <term><replaceable class="PARAMETER">table_name</replaceable></term>
  78     <listitem>
  79      <para>
  80       The (possibly schema-qualified) name of the table in which
  81       the triggering events occur.
  82      </para>
  83     </listitem>
  84    </varlistentry>
  85
  86    <varlistentry>
  87     <term><replaceable class="PARAMETER">referenced_table_name</replaceable></term>
  88     <listitem>
  89      <para>
  90       The (possibly schema-qualified) name of another table referenced by the
  91       constraint.  This option is used for foreign-key constraints and is not
  92       recommended for general use.
  93      </para>
  94     </listitem>
  95    </varlistentry>
  96
  97    <varlistentry>
  98     <term><literal>DEFERRABLE</literal></term>
  99     <term><literal>NOT DEFERRABLE</literal></term>
 100     <term><literal>INITIALLY IMMEDIATE</literal></term>
 101     <term><literal>INITIALLY DEFERRED</literal></term>
 102     <listitem>
 103      <para>
 104       The default timing of the trigger.
 105       See the <xref linkend="SQL-CREATETABLE" endterm="SQL-CREATETABLE-TITLE">
 106       documentation for details of these constraint options.
 107      </para>
 108     </listitem>
 109    </varlistentry>
 110
 111    <varlistentry>
 112     <term><replaceable class="PARAMETER">funcname</replaceable></term>
 113     <listitem>
 114      <para>
 115       The function to call when the trigger is fired. See <xref
 116       linkend="SQL-CREATETRIGGER" endterm="SQL-CREATETRIGGER-TITLE"> for
 117       details.
 118      </para>
 119     </listitem>
 120    </varlistentry>
 121
 122    <varlistentry>
 123     <term><replaceable class="PARAMETER">arguments</replaceable></term>
 124     <listitem>
 125      <para>
 126       Optional argument strings to pass to the trigger function. See <xref
 127       linkend="SQL-CREATETRIGGER" endterm="SQL-CREATETRIGGER-TITLE"> for
 128       details.
 129      </para>
 130     </listitem>
 131    </varlistentry>
 132   </variablelist>
 133   </refsect1>
 134
 135  <refsect1>
 136   <title>Compatibility</title>
 137   <para>
 138    <command>CREATE CONSTRAINT TRIGGER</command> is a
 139    <productname>PostgreSQL</productname> extension of the <acronym>SQL</>
 140    standard.
 141   </para>
 142  </refsect1>
 143
 144  <refsect1>
 145   <title>See Also</title>
 146
 147   <simplelist type="inline">
 148    <member><xref linkend="sql-createtrigger" endterm="sql-createtrigger-title"></member>
 149    <member><xref linkend="sql-droptrigger" endterm="sql-droptrigger-title"></member>
 150    <member><xref linkend="sql-set-constraints" endterm="sql-set-constraints-title"></member>
 151   </simplelist>
 152  </refsect1>
 153 </refentry>