<!--
$Header: /cvsroot/pgsql/doc/src/sgml/ref/create_schema.sgml,v 1.4 2003/02/03 15:56:50 momjian Exp $
PostgreSQL documentation
-->

<refentry id="SQL-CREATESCHEMA">
 <refmeta>
  <refentrytitle id="sql-createschema-title">CREATE SCHEMA</refentrytitle>
  <refmiscinfo>SQL - Language Statements</refmiscinfo>
 </refmeta>
 <refnamediv>
  <refname>
   CREATE SCHEMA
  </refname>
  <refpurpose>
   define a new schema
  </refpurpose>
 </refnamediv> 
 <refsynopsisdiv>
  <synopsis>
CREATE SCHEMA <replaceable class="parameter">schemaname</replaceable> [ AUTHORIZATION <replaceable class="parameter">username</replaceable> ] [ <replaceable class="parameter">schema_element</replaceable> [ ... ] ]
CREATE SCHEMA AUTHORIZATION <replaceable class="parameter">username</replaceable> [ <replaceable class="parameter">schema_element</replaceable> [ ... ] ]
  </synopsis>
  
  <refsect2 id="R2-SQL-CREATESCHEMA-1">
   <title>
    Inputs
   </title>
   <para>

    <variablelist>
     <varlistentry>
      <term><replaceable class="parameter">schemaname</replaceable></term>
      <listitem>
       <para>
	The name of a schema to be created.  If this is omitted, the user name
	is used as the schema name.
       </para>
      </listitem>
     </varlistentry>

     <varlistentry>
      <term><replaceable class="parameter">username</replaceable></term>
      <listitem>
       <para>
        The name of the user who will own the schema.  If omitted,
	defaults to the user executing the command.  Only superusers
	may create schemas owned by users other than themselves.
       </para>
      </listitem>
     </varlistentry>

     <varlistentry>
      <term><replaceable class="parameter">schema_element</replaceable></term>
      <listitem>
       <para>
        An SQL statement defining an object to be created within the schema.
	Currently, only <command>CREATE TABLE</>, <command>CREATE VIEW</>, 
	and <command>GRANT</> are accepted as clauses within
	<command>CREATE SCHEMA</>.  Other kinds of objects may be created
	in separate commands after the schema is created.
       </para>
      </listitem>
     </varlistentry>
    </variablelist>
   </para>
  </refsect2>

  <refsect2 id="R2-SQL-CREATESCHEMA-2">
   <title>
    Outputs
   </title>
   <para>

    <variablelist>
     <varlistentry>
      <term><computeroutput>
CREATE SCHEMA
       </computeroutput></term>
      <listitem>
       <para>
	Message returned if the command is successful.
       </para>
      </listitem>
     </varlistentry>
     <varlistentry>
      <term><computeroutput>
ERROR:  namespace "<replaceable class="parameter">schemaname</replaceable>" already exists
       </computeroutput></term>
      <listitem>
       <para>
	If the schema specified already exists.
       </para>
      </listitem>
     </varlistentry>
    </variablelist>
   </para>
  </refsect2>
 </refsynopsisdiv>

 <refsect1 id="R1-SQL-CREATESCHEMA-1">
  <title>
   Description
  </title>
  <para>
   <command>CREATE SCHEMA</command> will enter a new schema
   into the current database.
   The schema name must be distinct from the name of any existing schema
   in the current database.
  </para>

  <para>
   A schema is essentially a namespace:
   it contains named objects (tables, data types, functions, and operators)
   whose names may duplicate those of other objects existing in other
   schemas.  Named objects are accessed either by <quote>qualifying</>
   their names with the schema name as a prefix, or by setting a search
   path that includes the desired schema(s).  Unqualified objects are
   created in the current schema (the one at the front of the search path; 
   see <literal>CURRENT_SCHEMA()</>).
  </para>

  <para>
   Optionally, <command>CREATE SCHEMA</command> can include subcommands
   to create objects within the new schema.  The subcommands are treated
   essentially the same as separate commands issued after creating the
   schema, except that if the <literal>AUTHORIZATION</> clause is used,
   all the created objects will be owned by that user.
  </para>

  <refsect2 id="R2-SQL-CREATESCHEMA-3">
   <title>
    Notes
   </title>

   <para>
    To create a schema, the invoking user must have <literal>CREATE</>
    privilege for the current database.  (Of course, superusers bypass
    this check.)
   </para>

   <para>
    Use <command>DROP SCHEMA</command> to remove a schema.
   </para>
  </refsect2>
 </refsect1>

 <refsect1 id="R1-SQL-CREATESCHEMA-2">
  <title>
   Examples
  </title>
  <para>
   Create a schema:

  <programlisting>
CREATE SCHEMA myschema;
  </programlisting>
  </para>

  <para>
   Create a schema for user <literal>joe</> --- the schema will also
   be named <literal>joe</>:

  <programlisting>
CREATE SCHEMA AUTHORIZATION joe;
  </programlisting>
  </para>

  <para>
   Create a schema and create a table and view within it:

  <programlisting>
CREATE SCHEMA hollywood
    CREATE TABLE films (title text, release date, awards text[])
    CREATE VIEW winners AS
        SELECT title, release FROM films WHERE awards IS NOT NULL;
  </programlisting>
   Notice that the individual subcommands do not end with semicolons.
  </para>

  <para>
   The following is an equivalent way of accomplishing the same result:
  <programlisting>
CREATE SCHEMA hollywood;
CREATE TABLE hollywood.films (title text, release date, awards text[]);
CREATE VIEW hollywood.winners AS
    SELECT title, release FROM hollywood.films WHERE awards IS NOT NULL;
  </programlisting>
  </para>
 </refsect1>

 <refsect1 id="R1-SQL-CREATESCHEMA-3">
  <title>
   Compatibility
  </title>

  <refsect2 id="R2-SQL-CREATESCHEMA-4">
   <title>
    SQL92
   </title>

   <para>
    SQL92 allows a <literal>DEFAULT CHARACTER SET</> clause in
    <command>CREATE SCHEMA</command>, as well as more subcommand types
    than are presently accepted by <productname>PostgreSQL</productname>.
   </para>

   <para>
    SQL92 specifies that the subcommands in <command>CREATE SCHEMA</command>
    may appear in any order.  The present
    <productname>PostgreSQL</productname> implementation does not handle all
    cases of forward references in subcommands; it may sometimes be necessary
    to reorder the subcommands to avoid forward references.
   </para>

   <para>
    In SQL92, the owner of a schema always owns all objects within it.
    <productname>PostgreSQL</productname> allows schemas to contain objects
    owned by users other than the schema owner.  This can happen only if the
    schema owner grants <literal>CREATE</> rights on his schema to someone
    else.
   </para>
  </refsect2>
 </refsect1>
</refentry>

<!-- Keep this comment at the end of the file
Local variables:
mode: sgml
sgml-omittag:nil
sgml-shorttag:t
sgml-minimize-attributes:nil
sgml-always-quote-attributes:t
sgml-indent-step:1
sgml-indent-data:t
sgml-parent-document:nil
sgml-default-dtd-file:"../reference.ced"
sgml-exposed-tags:nil
sgml-local-catalogs:"/usr/lib/sgml/catalog"
sgml-local-ecat-files:nil
End:
-->
