grant.sgml

<!--
$Header: /cvsroot/pgsql/doc/src/sgml/ref/grant.sgml,v 1.31 2002/11/21 23:34:43 petere Exp $
PostgreSQL documentation
-->

<refentry id="SQL-GRANT">
 <refmeta>
  <refentrytitle id="sql-grant-title">GRANT</refentrytitle>
  <refmiscinfo>SQL - Language Statements</refmiscinfo>
 </refmeta>

 <refnamediv>
  <refname>GRANT</refname>
  <refpurpose>define access privileges</refpurpose>
 </refnamediv>

 <refsynopsisdiv>
<synopsis>
GRANT { { SELECT | INSERT | UPDATE | DELETE | RULE | REFERENCES | TRIGGER }
    [,...] | ALL [ PRIVILEGES ] }
    ON [ TABLE ] <replaceable class="PARAMETER">tablename</replaceable> [, ...]
    TO { <replaceable class="PARAMETER">username</replaceable> | GROUP <replaceable class="PARAMETER">groupname</replaceable> | PUBLIC } [, ...]

GRANT { { CREATE | TEMPORARY | TEMP } [,...] | ALL [ PRIVILEGES ] }
    ON DATABASE <replaceable>dbname</replaceable> [, ...]
    TO { <replaceable class="PARAMETER">username</replaceable> | GROUP <replaceable class="PARAMETER">groupname</replaceable> | PUBLIC } [, ...]

GRANT { EXECUTE | ALL [ PRIVILEGES ] }
    ON FUNCTION <replaceable>funcname</replaceable> ([<replaceable>type</replaceable>, ...]) [, ...]
    TO { <replaceable class="PARAMETER">username</replaceable> | GROUP <replaceable class="PARAMETER">groupname</replaceable> | PUBLIC } [, ...]

GRANT { USAGE | ALL [ PRIVILEGES ] }
    ON LANGUAGE <replaceable>langname</replaceable> [, ...]
    TO { <replaceable class="PARAMETER">username</replaceable> | GROUP <replaceable class="PARAMETER">groupname</replaceable> | PUBLIC } [, ...]

GRANT { { CREATE | USAGE } [,...] | ALL [ PRIVILEGES ] }
    ON SCHEMA <replaceable>schemaname</replaceable> [, ...]
    TO { <replaceable class="PARAMETER">username</replaceable> | GROUP <replaceable class="PARAMETER">groupname</replaceable> | PUBLIC } [, ...]
</synopsis>
 </refsynopsisdiv>

 <refsect1 id="sql-grant-description">
  <title>Description</title>

  <para>
   The <command>GRANT</command> command gives specific permissions on
   an object (table, view, sequence, database, function, procedural language,
   or schema) to
   one or more users or groups of users.  These permissions are added
   to those already granted, if any.
  </para>

  <para>
   The key word <literal>PUBLIC</literal> indicates that the
   privileges are to be granted to all users, including those that may
   be created later.  <literal>PUBLIC</literal> may be thought of as an
   implicitly defined group that always includes all users.
   Note that any particular user will have the sum
   of privileges granted directly to him, privileges granted to any group he
   is presently a member of, and privileges granted to
   <literal>PUBLIC</literal>.
  </para>

  <para>
   There is no need to grant privileges to the creator of an object,
   as the creator has all privileges by default.
   (The creator could, however, choose to revoke
   some of his own privileges for safety.)  Note that the ability to
   grant and revoke privileges is inherent in the creator and cannot
   be lost.  The right to drop an object, or to alter it in any way
   not described by a grantable right, is likewise inherent in the
   creator, and cannot be granted or revoked.
  </para>

  <para>
   Depending on the type of object, the initial default privileges may
   include granting some privileges to <literal>PUBLIC</literal>.
   The default is no public access for tables and schemas;
   <literal>TEMP</> table creation privilege for databases;
   <literal>EXECUTE</> privilege for functions; and
   <literal>USAGE</> privilege for languages.
   The object creator may of course revoke these privileges.  (For maximum
   security, issue the <command>REVOKE</> in the same transaction that
   creates the object; then there is no window in which another user
   may use the object.)
  </para>

  <para>
   The possible privileges are:

   <variablelist>
    <varlistentry>
     <term>SELECT</term>
     <listitem>
      <para>
       Allows <xref linkend="sql-select" endterm="sql-select-title"> from any column of the
       specified table, view, or sequence.  Also allows the use of
       <xref linkend="sql-copy" endterm="sql-copy-title"> TO.  For sequences, this
       privilege also allows the use of the <function>currval</function> function.
      </para>
     </listitem>
    </varlistentry>

    <varlistentry>
     <term>INSERT</term>
     <listitem>
      <para>
       Allows <xref linkend="sql-insert" endterm="sql-insert-title"> of a new row into the
       specified table.  Also allows <xref linkend="sql-copy" endterm="sql-copy-title"> FROM.
      </para>
     </listitem>
    </varlistentry>

    <varlistentry>
     <term>UPDATE</term>
     <listitem>
      <para>
       Allows <xref linkend="sql-update" endterm="sql-update-title"> of any column of the
       specified table.  <literal>SELECT ... FOR UPDATE</literal>
       also requires this privilege (besides the
       <literal>SELECT</literal> privilege).  For sequences, this
       privilege allows the use of the <function>nextval</function> and
       <function>setval</function> functions.
      </para>
     </listitem>
    </varlistentry>

    <varlistentry>
     <term>DELETE</term>
     <listitem>
      <para>
       Allows <xref linkend="sql-delete" endterm="sql-delete-title"> of a row from the
       specified table.
      </para>
     </listitem>
    </varlistentry>

    <varlistentry>
     <term>RULE</term>
     <listitem>
      <para>
       Allows the creation of a rule on the table/view.  (See <xref
       linkend="sql-createrule" endterm="sql-createrule-title"> statement.)
      </para>
     </listitem>
    </varlistentry>

    <varlistentry>
     <term>REFERENCES</term>
     <listitem>
      <para>
       To create a foreign key constraint, it is
       necessary to have this privilege on both the referencing and
       referenced tables.
      </para>
     </listitem>
    </varlistentry>

    <varlistentry>
     <term>TRIGGER</term>
     <listitem>
      <para>
       Allows the creation of a trigger on the specified table.  (See
       <xref linkend="sql-createtrigger" endterm="sql-createtrigger-title"> statement.)
      </para>
     </listitem>
    </varlistentry>

    <varlistentry>
     <term>CREATE</term>
     <listitem>
      <para>
       For databases, allows new schemas to be created within the database.
      </para>
      <para>
       For schemas, allows new objects to be created within the schema.
       To rename an existing object, you must own the object <emphasis>and</>
       have this privilege for the containing schema.
      </para>
     </listitem>
    </varlistentry>

    <varlistentry>
     <term>TEMPORARY</term>
     <term>TEMP</term>
     <listitem>
      <para>
       Allows temporary tables to be created while using the database.
      </para>
     </listitem>
    </varlistentry>

    <varlistentry>
     <term>EXECUTE</term>
     <listitem>
      <para>
       Allows the use of the specified function and the use of any
       operators that are implemented on top of the function.  This is
       the only type of privilege that is applicable to functions.
       (This syntax works for aggregate functions, as well.)
      </para>
     </listitem>
    </varlistentry>

    <varlistentry>
     <term>USAGE</term>
     <listitem>
      <para>
       For procedural languages, allows the use of the specified language for
       the creation of functions in that language.  This is the only type
       of privilege that is applicable to procedural languages.
      </para>
      <para>
       For schemas, allows access to objects contained in the specified 
       schema (assuming that the objects' own privilege requirements are
       also met).  Essentially this allows the grantee to <quote>look up</>
       objects within the schema.
      </para>
     </listitem>
    </varlistentry>

    <varlistentry>
     <term>ALL PRIVILEGES</term>
     <listitem>
      <para>
       Grant all of the privileges applicable to the object at once.
       The <literal>PRIVILEGES</literal> key word is optional in
       <productname>PostgreSQL</productname>, though it is required by
       strict SQL.
      </para>
     </listitem>
    </varlistentry>
   </variablelist>

   The privileges required by other commands are listed on the
   reference page of the respective command.
  </para>
 </refsect1>


 <refsect1 id="SQL-GRANT-notes">
  <title>Notes</title>

   <para>
    The <xref linkend="sql-revoke" endterm="sql-revoke-title"> command is used
    to revoke access privileges.
   </para>

   <para>
    It should be noted that database <firstterm>superusers</> can access
    all objects regardless of object privilege settings.  This
    is comparable to the rights of <literal>root</> in a Unix system.
    As with <literal>root</>, it's unwise to operate as a superuser
    except when absolutely necessary.
   </para>

   <para>
    Currently, to grant privileges in <productname>PostgreSQL</productname>
    to only a few columns, you must
    create a view having the desired columns and then grant privileges
    to that view.
   </para>

   <para>
    Use <xref linkend="app-psql">'s <command>\dp</command> command
    to obtain information about existing privileges, for example:
<programlisting>
lusitania=> \dp mytable
        Access privileges for database "lusitania"
 Schema |  Table  |           Access privileges
--------+---------+---------------------------------------
 public | mytable | {=r,miriam=arwdRxt,"group todos=arw"}
(1 row)
</programlisting>
    The entries shown by <command>\dp</command> are interpreted thus:
<programlisting>
              =xxxx -- privileges granted to PUBLIC
         uname=xxxx -- privileges granted to a user
   group gname=xxxx -- privileges granted to a group

                  r -- SELECT ("read")
                  w -- UPDATE ("write")
                  a -- INSERT ("append")
                  d -- DELETE
                  R -- RULE
                  x -- REFERENCES
                  t -- TRIGGER
                  X -- EXECUTE
                  U -- USAGE
                  C -- CREATE
                  T -- TEMPORARY
            arwdRxt -- ALL PRIVILEGES (for tables)
</programlisting>

    The above example display would be seen by user <literal>miriam</> after
    creating table <literal>mytable</> and doing

<programlisting>
GRANT SELECT ON mytable TO PUBLIC;
GRANT SELECT,UPDATE,INSERT ON mytable TO GROUP todos;
</programlisting>
   </para>

   <para>
   If the <quote>Access privileges</> column is empty for a given object,
it means the object has default privileges (that is, its privileges field
is NULL).  Default privileges always include all privileges for the owner,
and may include some privileges for <literal>PUBLIC</> depending on the
object type, as explained above.  The first <command>GRANT</> or
<command>REVOKE</> on an object
will instantiate the default privileges (producing, for example,
<literal>{=,miriam=arwdRxt}</>) and then modify them per the specified request.
   </para>
 </refsect1>

 <refsect1 id="sql-grant-examples">
  <title>Examples</title>

  <para>
   Grant insert privilege to all users on table films:

<programlisting>
GRANT INSERT ON films TO PUBLIC;
</programlisting>
  </para>

  <para>
   Grant all privileges to user <literal>manuel</literal> on view <literal>kinds</literal>:

<programlisting>
GRANT ALL PRIVILEGES ON kinds TO manuel;
</programlisting>
  </para>
 </refsect1>

 <refsect1 id="sql-grant-compatibility">
  <title>Compatibility</title>
    
  <refsect2>
   <title>SQL92</title>

   <para>
    The <literal>PRIVILEGES</literal> key word in <literal>ALL
    PRIVILEGES</literal> is required.  <acronym>SQL</acronym> does not
    support setting the privileges on more than one table per command.
   </para>

   <para>
    The <acronym>SQL92</acronym> syntax for GRANT allows setting
    privileges for individual columns within a table, and allows
    setting a privilege to grant the same privileges to others:

<synopsis>
GRANT <replaceable class="PARAMETER">privilege</replaceable> [, ...]
    ON <replaceable class="PARAMETER">object</replaceable> [ ( <replaceable class="PARAMETER">column</replaceable> [, ...] ) ] [, ...]
    TO { PUBLIC | <replaceable class="PARAMETER">username</replaceable> [, ...] } [ WITH GRANT OPTION ]
</synopsis>
   </para>

   <para>
    <acronym>SQL</acronym> allows to grant the USAGE privilege on
    other kinds of objects:  CHARACTER SET, COLLATION, TRANSLATION, DOMAIN.
   </para>

   <para>
    The TRIGGER privilege was introduced in SQL99.  The RULE privilege
    is a PostgreSQL extension.
   </para>
  </refsect2>

 </refsect1>


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

  <simpara>
   <xref linkend="sql-revoke" endterm="sql-revoke-title">
  </simpara>
 </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:
-->