The identifier serves as the <quote>variable name</quote> of the
    descriptor area.  <!-- The scope of the allocated descriptor is WHAT?. -->
    When you don't need the descriptor anymore, you should deallocate
    it:
<programlisting>
EXEC SQL DEALLOCATE DESCRIPTOR <replaceable>identifier</replaceable>;
</programlisting>
   </para>

   <para>
    To use a descriptor area, specify it as the storage target in an
    <literal>INTO</literal> clause, instead of listing host variables:
<programlisting>
EXEC SQL FETCH NEXT FROM mycursor INTO SQL DESCRIPTOR mydesc;
</programlisting>
    If the result set is empty, the Descriptor Area will still contain
    the metadata from the query, i.e., the field names.
   </para>

   <para>
    For not yet executed prepared queries, the <command>DESCRIBE</command>
    statement can be used to get the metadata of the result set:
<programlisting>
EXEC SQL BEGIN DECLARE SECTION;
char *sql_stmt = "SELECT * FROM table1";
EXEC SQL END DECLARE SECTION;

EXEC SQL PREPARE stmt1 FROM :sql_stmt;
EXEC SQL DESCRIBE stmt1 INTO SQL DESCRIPTOR mydesc;
</programlisting>
   </para>

   <para>
    Before PostgreSQL 9.0, the <literal>SQL</literal> keyword was optional,
    so using <literal>DESCRIPTOR</literal> and <literal>SQL DESCRIPTOR</literal>
    produced named SQL Descriptor Areas. Now it is mandatory, omitting
    the <literal>SQL</literal> keyword produces SQLDA Descriptor Areas,
    see <xref linkend="ecpg-sqlda-descriptors"/>.
   </para>

   <para>
    In <command>DESCRIBE</command> and <command>FETCH</command> statements,
    the <literal>INTO</literal> and <literal>USING</literal> keywords can be
    used to similarly: they produce the result set and the metadata in a
    Descriptor Area.
   </para>

   <para>
    Now how do you get the data out of the descriptor area?  You can
    think of the descriptor area as a structure with named fields.  To
    retrieve the value of a field from the header and store it into a
    host variable, use the following command:
<programlisting>
EXEC SQL GET DESCRIPTOR <replaceable>name</replaceable> :<replaceable>hostvar</replaceable> = <replaceable>field</replaceable>;
</programlisting>
    Currently, there is only one header field defined:
    <replaceable>COUNT</replaceable>, which tells how many item
    descriptor areas exist (that is, how many columns are contained in
    the result).  The host variable needs to be of an integer type.  To
    get a field from the item descriptor area, use the following
    command:
<programlisting>
EXEC SQL GET DESCRIPTOR <replaceable>name</replaceable> VALUE <replaceable>num</replaceable> :<replaceable>hostvar</replaceable> = <replaceable>field</replaceable>;
</programlisting>
    <replaceable>num</replaceable> can be a literal integer or a host
    variable containing an integer. Possible fields are:

    <variablelist>
     <varlistentry id="ecpg-named-descriptors-cardinality">
      <term><literal>CARDINALITY</literal> (integer)</term>
      <listitem>
       <para>
        number of rows in the result set
       </para>
      </listitem>
     </varlistentry>

     <varlistentry id="ecpg-named-descriptors-data">
      <term><literal>DATA</literal></term>
      <listitem>
       <para>
        actual data item (therefore, the data type of this field
        depends on the query)
       </para>
      </listitem>
     </varlistentry>

     <varlistentry id="ecpg-named-descriptors-datetime-interval-code">
      <term><literal>DATETIME_INTERVAL_CODE</literal> (integer)</term>
      <listitem>
       <para>
        When <literal>TYPE</literal> is <literal>9</literal>,
        <literal>DATETIME_INTERVAL_CODE</literal> will have a value of
        <literal>1</literal> for <literal>DATE</literal>,
        <literal>2</literal> for <literal>TIME</literal>,
        <literal>3</literal> for <literal>TIMESTAMP</literal>,
        <literal>4</literal> for <literal>TIME WITH TIME ZONE</literal>, or
        <literal>5</literal> for <literal>TIMESTAMP