<para>
        Returns first starting index of the specified <parameter>substring</parameter>
        within <parameter>bits</parameter>, or zero if it's not present.
       </para>
       <para>
        <literal>position(B'010' in B'000001101011')</literal>
        <returnvalue>8</returnvalue>
       </para></entry>
      </row>

      <row>
       <entry role="func_table_entry"><para role="func_signature">
        <indexterm>
         <primary>substring</primary>
        </indexterm>
        <function>substring</function> ( <parameter>bits</parameter> <type>bit</type> <optional> <literal>FROM</literal> <parameter>start</parameter> <type>integer</type> </optional> <optional> <literal>FOR</literal> <parameter>count</parameter> <type>integer</type> </optional> )
        <returnvalue>bit</returnvalue>
       </para>
       <para>
        Extracts the substring of <parameter>bits</parameter> starting at
        the <parameter>start</parameter>'th bit if that is specified,
        and stopping after <parameter>count</parameter> bits if that is
        specified.  Provide at least one of <parameter>start</parameter>
        and <parameter>count</parameter>.
       </para>
       <para>
        <literal>substring(B'110010111111' from 3 for 2)</literal>
        <returnvalue>00</returnvalue>
       </para></entry>
      </row>

      <row>
       <entry role="func_table_entry"><para role="func_signature">
        <indexterm>
         <primary>get_bit</primary>
        </indexterm>
        <function>get_bit</function> ( <parameter>bits</parameter> <type>bit</type>,
        <parameter>n</parameter> <type>integer</type> )
        <returnvalue>integer</returnvalue>
       </para>
       <para>
        Extracts <parameter>n</parameter>'th bit
        from bit string; the first (leftmost) bit is bit 0.
       </para>
       <para>
        <literal>get_bit(B'101010101010101010', 6)</literal>
        <returnvalue>1</returnvalue>
       </para></entry>
      </row>

      <row>
       <entry role="func_table_entry"><para role="func_signature">
        <indexterm>
         <primary>set_bit</primary>
        </indexterm>
        <function>set_bit</function> ( <parameter>bits</parameter> <type>bit</type>,
        <parameter>n</parameter> <type>integer</type>,
        <parameter>newvalue</parameter> <type>integer</type> )
        <returnvalue>bit</returnvalue>
       </para>
       <para>
        Sets <parameter>n</parameter>'th bit in
        bit string to <parameter>newvalue</parameter>;
        the first (leftmost) bit is bit 0.
       </para>
       <para>
        <literal>set_bit(B'101010101010101010', 6, 0)</literal>
        <returnvalue>101010001010101010</returnvalue>
       </para></entry>
      </row>
     </tbody>
    </tgroup>
   </table>

   <para>
    In addition, it is possible to cast integral values to and from type
    <type>bit</type>.
    Casting an integer to <type>bit(n)</type> copies the rightmost
    <literal>n</literal> bits.  Casting an integer to a bit string width wider
    than the integer itself will sign-extend on the left.
    Some examples:
<programlisting>
44::bit(10)                    <lineannotation>0000101100</lineannotation>
44::bit(3)                     <lineannotation>100</lineannotation>
cast(-44 as bit(12))           <lineannotation>111111010100</lineannotation>
'1110'::bit(4)::integer        <lineannotation>14</lineannotation>
</programlisting>
    Note that casting to just <quote>bit</quote> means casting to
    <literal>bit(1)</literal>, and so will deliver only the least significant
    bit of the integer.
   </para>
  </sect1>


 <sect1 id="functions-matching">
  <title>Pattern Matching</title>

  <indexterm zone="functions-matching">
   <primary>pattern matching</primary>
  </indexterm>

   <para>
    There are three separate approaches to pattern matching provided
    by <productname>PostgreSQL</productname>: the traditional
    <acronym>SQL</acronym> <function>LIKE</function> operator, the
    more