postgresql/doc/src/sgml/ref/set_constraints.sgml

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<refentry id="SQL-SET-CONSTRAINTS">
 <refmeta>
  <refentrytitle id="SQL-SET-CONSTRAINTS-title">SET CONSTRAINTS</refentrytitle>
  <refmiscinfo>SQL - Language Statements</refmiscinfo>
 </refmeta>
 <refnamediv>
  <refname>SET CONSTRAINTS</refname>
  <refpurpose>Set the constraint mode of the current SQL-transaction</refpurpose>
 </refnamediv>
 <refsynopsisdiv>
  <refsynopsisdivinfo>
   <date>2000-06-01</date>
  </refsynopsisdivinfo>
  <synopsis>
SET CONSTRAINTS { ALL | <replaceable class="parameter">constraint</replaceable> [, ...] } { DEFERRED | IMMEDIATE }
  </synopsis>
 </refsynopsisdiv>

 <refsect1>
  <title>Description</title>

  <para>
   <command>SET CONSTRAINTS</command> sets the behavior of constraint
   evaluation in the current transaction. In
   <option>IMMEDIATE</option> mode, constraints are checked at the end
   of each statement. In <option>DEFERRED</option> mode, constraints
   are not checked until transaction commit.
  </para>

  <para>
   Upon creation, a constraint is always give one of three
   characteristics: <option>INITIALLY DEFERRED</option>,
   <option>INITIALLY IMMEDIATE DEFERRABLE</option>, or
   <option>INITIALLY IMMEDIATE NOT DEFERRABLE</option>. The third
   class is not affected by the <command>SET CONSTRAINTS</command>
   command.
  </para>

  <para>
   Currently, only foreign key constraints are affected by this
   setting. Check and unique constraints are always effectively
   initially immediate not deferrable.
  </para>
 </refsect1>

 <refsect1>
  <title>Compatibility</title>
  <para>
   SQL92, SQL99
  </para>
 </refsect1>
</refentry>