create_schema.sgml

postgresql8.3.4源码,开源数据库

<!--
$PostgreSQL: pgsql/doc/src/sgml/ref/create_schema.sgml,v 1.19 2007/01/31 23:26:03 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>

 <indexterm zone="sql-createschema">
  <primary>CREATE SCHEMA</primary>
 </indexterm>

 <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>
 </refsynopsisdiv>

 <refsect1>
  <title>Description</title>

  <para>
   <command>CREATE SCHEMA</command> enters 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 can 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).  A <literal>CREATE</> command
   specifying an unqualified object name creates the object
   in the current schema (the one at the front of the search path,
   which can be determined with the function <function>current_schema</function>).
  </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>
 </refsect1>

 <refsect1>
  <title>Parameters</title>

    <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.  The name cannot
        begin with <literal>pg_</literal>, as such names
        are reserved for system schemas.
       </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
        can 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</>, <command>CREATE
        INDEX</>, <command>CREATE SEQUENCE</>, <command>CREATE
        TRIGGER</> 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>
 </refsect1>

 <refsect1>
  <title>Notes</title>

  <para>
   To create a schema, the invoking user must have the
   <literal>CREATE</> privilege for the current database.
   (Of course, superusers bypass this check.)
  </para>
 </refsect1>

 <refsect1>
  <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>
  <title>Compatibility</title>

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

  <para>
   According to the SQL standard, 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 the
   <literal>CREATE</> privilege on his schema to someone else.
  </para>
 </refsect1>

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

  <simplelist type="inline">
   <member><xref linkend="sql-alterschema" endterm="sql-alterschema-title"></member>
   <member><xref linkend="sql-dropschema" endterm="sql-dropschema-title"></member>
 </simplelist>
 </refsect1>

</refentry>