<!--
doc/src/sgml/ref/alter_domain.sgml
PostgreSQL documentation
-->

<refentry id="sql-alterdomain">
 <indexterm zone="sql-alterdomain">
  <primary>ALTER DOMAIN</primary>
 </indexterm>

 <refmeta>
  <refentrytitle>ALTER DOMAIN</refentrytitle>
  <manvolnum>7</manvolnum>
  <refmiscinfo>SQL - Language Statements</refmiscinfo>
 </refmeta>

 <refnamediv>
  <refname>ALTER DOMAIN</refname>
  <refpurpose>
   change the definition of a domain
  </refpurpose>
 </refnamediv>

 <refsynopsisdiv>
<synopsis>
ALTER DOMAIN <replaceable class="parameter">name</replaceable>
    { SET DEFAULT <replaceable class="parameter">expression</replaceable> | DROP DEFAULT }
ALTER DOMAIN <replaceable class="parameter">name</replaceable>
    { SET | DROP } NOT NULL
ALTER DOMAIN <replaceable class="parameter">name</replaceable>
    ADD <replaceable class="parameter">domain_constraint</replaceable> [ NOT VALID ]
ALTER DOMAIN <replaceable class="parameter">name</replaceable>
    DROP CONSTRAINT [ IF EXISTS ] <replaceable class="parameter">constraint_name</replaceable> [ RESTRICT | CASCADE ]
ALTER DOMAIN <replaceable class="parameter">name</replaceable>
     RENAME CONSTRAINT <replaceable class="parameter">constraint_name</replaceable> TO <replaceable class="parameter">new_constraint_name</replaceable>
ALTER DOMAIN <replaceable class="parameter">name</replaceable>
    VALIDATE CONSTRAINT <replaceable class="parameter">constraint_name</replaceable>
ALTER DOMAIN <replaceable class="parameter">name</replaceable>
    OWNER TO { <replaceable class="parameter">new_owner</replaceable> | CURRENT_ROLE | CURRENT_USER | SESSION_USER }
ALTER DOMAIN <replaceable class="parameter">name</replaceable>
    RENAME TO <replaceable class="parameter">new_name</replaceable>
ALTER DOMAIN <replaceable class="parameter">name</replaceable>
    SET SCHEMA <replaceable class="parameter">new_schema</replaceable>

<phrase>where <replaceable class="parameter">domain_constraint</replaceable> is:</phrase>

[ CONSTRAINT <replaceable class="parameter">constraint_name</replaceable> ]
{ NOT NULL | CHECK (<replaceable class="parameter">expression</replaceable>) }
</synopsis>
 </refsynopsisdiv>

 <refsect1>
  <title>Description</title>

  <para>
   <command>ALTER DOMAIN</command> changes the definition of an existing domain.
   There are several sub-forms:
  </para>

  <variablelist>
   <varlistentry>
    <term><literal>SET</literal>/<literal>DROP DEFAULT</literal></term>
    <listitem>
     <para>
      These forms set or remove the default value for a domain. Note
      that defaults only apply to subsequent <command>INSERT</command>
      commands; they do not affect rows already in a table using the domain.
     </para>
    </listitem>
   </varlistentry>

   <varlistentry>
    <term><literal>SET</literal>/<literal>DROP NOT NULL</literal></term>
    <listitem>
     <para>
      These forms change whether a domain is marked to allow NULL
      values or to reject NULL values.  You can only <literal>SET NOT NULL</literal>
      when the columns using the domain contain no null values.
     </para>
    </listitem>
   </varlistentry>

   <varlistentry>
    <term><literal>ADD <replaceable class="parameter">domain_constraint</replaceable> [ NOT VALID ]</literal></term>
    <listitem>
     <para>
      This form adds a new constraint to a domain.
      When a new constraint is added to a domain, all columns using that
      domain will be checked against the newly added constraint.  These
      checks can be suppressed by adding the new constraint using the
      <literal>NOT VALID</literal> option; the constraint can later be made
      valid using <command>ALTER DOMAIN ... VALIDATE CONSTRAINT</command>.
      Newly inserted or updated rows are always checked against all
      constraints, even those marked <literal>NOT VALID</literal>.
      <literal>NOT VALID</literal> is only accepted for <literal>CHECK</literal> constraints.
     </para>
    </listitem>
   </varlistentry>

   <varlistentry>
    <term><literal>DROP