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

<refentry id="sql-alterview">
 <indexterm zone="sql-alterview">
  <primary>ALTER VIEW</primary>
 </indexterm>

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

 <refnamediv>
  <refname>ALTER VIEW</refname>
  <refpurpose>change the definition of a view</refpurpose>
 </refnamediv>

 <refsynopsisdiv>
<synopsis>
ALTER VIEW [ IF EXISTS ] <replaceable class="parameter">name</replaceable> ALTER [ COLUMN ] <replaceable class="parameter">column_name</replaceable> SET DEFAULT <replaceable class="parameter">expression</replaceable>
ALTER VIEW [ IF EXISTS ] <replaceable class="parameter">name</replaceable> ALTER [ COLUMN ] <replaceable class="parameter">column_name</replaceable> DROP DEFAULT
ALTER VIEW [ IF EXISTS ] <replaceable class="parameter">name</replaceable> OWNER TO { <replaceable class="parameter">new_owner</replaceable> | CURRENT_ROLE | CURRENT_USER | SESSION_USER }
ALTER VIEW [ IF EXISTS ] <replaceable class="parameter">name</replaceable> RENAME [ COLUMN ] <replaceable class="parameter">column_name</replaceable> TO <replaceable class="parameter">new_column_name</replaceable>
ALTER VIEW [ IF EXISTS ] <replaceable class="parameter">name</replaceable> RENAME TO <replaceable class="parameter">new_name</replaceable>
ALTER VIEW [ IF EXISTS ] <replaceable class="parameter">name</replaceable> SET SCHEMA <replaceable class="parameter">new_schema</replaceable>
ALTER VIEW [ IF EXISTS ] <replaceable class="parameter">name</replaceable> SET ( <replaceable class="parameter">view_option_name</replaceable> [= <replaceable class="parameter">view_option_value</replaceable>] [, ... ] )
ALTER VIEW [ IF EXISTS ] <replaceable class="parameter">name</replaceable> RESET ( <replaceable class="parameter">view_option_name</replaceable> [, ... ] )
</synopsis>
 </refsynopsisdiv>

 <refsect1>
  <title>Description</title>

  <para>
   <command>ALTER VIEW</command> changes various auxiliary properties
   of a view.  (If you want to modify the view's defining query,
   use <command>CREATE OR REPLACE VIEW</command>.)
  </para>

  <para>
   You must own the view to use <command>ALTER VIEW</command>.
   To change a view's schema, you must also have <literal>CREATE</literal>
   privilege on the new schema.
   To alter the owner, you must be able to <literal>SET ROLE</literal> to the
   new owning role, and that role must have <literal>CREATE</literal>
   privilege on the view's schema.
   (These restrictions enforce that altering the owner
   doesn't do anything you couldn't do by dropping and recreating the view.
   However, a superuser can alter ownership of any view anyway.)
  </para>
 </refsect1>

 <refsect1>
  <title>Parameters</title>

  <variablelist>
   <varlistentry>
    <term><replaceable class="parameter">name</replaceable></term>
    <listitem>
     <para>
      The name (optionally schema-qualified) of an existing view.
     </para>
    </listitem>
   </varlistentry>

   <varlistentry>
    <term><replaceable class="parameter">column_name</replaceable></term>
    <listitem>
     <para>
      Name of an existing column.
     </para>
    </listitem>
   </varlistentry>

   <varlistentry>
    <term><replaceable class="parameter">new_column_name</replaceable></term>
    <listitem>
     <para>
      New name for an existing column.
     </para>
    </listitem>
   </varlistentry>

   <varlistentry>
    <term><literal>IF EXISTS</literal></term>
    <listitem>
     <para>
      Do not throw an error if the view does not exist. A notice is issued
      in this case.
     </para>
    </listitem>
   </varlistentry>

   <varlistentry>
    <term><literal>SET</literal>/<literal>DROP DEFAULT</literal></term>
    <listitem>
     <para>
      These forms set or remove the default value for a column.
      A view column's default value is substituted into any
      <command>INSERT</command> or <command>UPDATE</command> command whose target is the
      view, before applying any rules or triggers for the view.  The view's
      default will therefore take precedence over any default values from
      underlying relations.
     </para>
    </listitem>
   </varlistentry>

   <varlistentry>
    <term><replaceable class="parameter">new_owner</replaceable></term>
    <listitem>
     <para>
      The user name of the new owner of the view.
     </para>
    </listitem>
   </varlistentry>

   <varlistentry>
    <term><replaceable class="parameter">new_name</replaceable></term>
    <listitem>
     <para>
      The new name for the view.
     </para>
    </listitem>
   </varlistentry>

   <varlistentry>
    <term><replaceable class="parameter">new_schema</replaceable></term>
    <listitem>
     <para>
      The new schema for the view.
     </para>
    </listitem>
   </varlistentry>

   <varlistentry>
    <term><literal>SET ( <replaceable class="parameter">view_option_name</replaceable> [= <replaceable class="parameter">view_option_value</replaceable>] [, ... ] )</literal></term>
    <term><literal>RESET ( <replaceable class="parameter">view_option_name</replaceable> [, ... ] )</literal></term>
    <listitem>
     <para>
      Sets or resets a view option.  Currently supported options are:
      <variablelist>
       <varlistentry>
        <term><literal>check_option</literal> (<type>enum</type>)</term>
        <listitem>
         <para>
          Changes the check option of the view.  The value must
          be <literal>local</literal> or <literal>cascaded</literal>.
         </para>
        </listitem>
       </varlistentry>
       <varlistentry>
        <term><literal>security_barrier</literal> (<type>boolean</type>)</term>
        <listitem>
         <para>
          Changes the security-barrier property of the view.  The value must
          be a Boolean value, such as <literal>true</literal>
          or <literal>false</literal>.
         </para>
        </listitem>
       </varlistentry>
       <varlistentry>
        <term><literal>security_invoker</literal> (<type>boolean</type>)</term>
        <listitem>
         <para>
          Changes the security-invoker property of the view.  The value must
          be a Boolean value, such as <literal>true</literal>
          or <literal>false</literal>.
         </para>
        </listitem>
       </varlistentry>
      </variablelist></para>
    </listitem>
   </varlistentry>
  </variablelist>
 </refsect1>

 <refsect1>
  <title>Notes</title>

  <para>
   For historical reasons, <command>ALTER TABLE</command> can be used with
   views too; but the only variants of <command>ALTER TABLE</command>
   that are allowed with views are equivalent to the ones shown above.
  </para>
 </refsect1>

 <refsect1>
  <title>Examples</title>

  <para>
   To rename the view <literal>foo</literal> to
   <literal>bar</literal>:
<programlisting>
ALTER VIEW foo RENAME TO bar;
</programlisting>
  </para>

  <para>
   To attach a default column value to an updatable view:
<programlisting>
CREATE TABLE base_table (id int, ts timestamptz);
CREATE VIEW a_view AS SELECT * FROM base_table;
ALTER VIEW a_view ALTER COLUMN ts SET DEFAULT now();
INSERT INTO base_table(id) VALUES(1);  -- ts will receive a NULL
INSERT INTO a_view(id) VALUES(2);  -- ts will receive the current time
</programlisting></para>
 </refsect1>

 <refsect1>
  <title>Compatibility</title>

  <para>
   <command>ALTER VIEW</command> is a <productname>PostgreSQL</productname>
   extension of the SQL standard.
  </para>
 </refsect1>

 <refsect1>
  <title>See Also</title>

  <simplelist type="inline">
   <member><xref linkend="sql-createview"/></member>
   <member><xref linkend="sql-dropview"/></member>
  </simplelist>
 </refsect1>
</refentry>
