BREs, this matches <replaceable>c</replaceable>) </entry>
       </row>

       <row>
       <entry> <literal>{</literal> </entry>
       <entry> when followed by a character other than a digit,
       matches the left-brace character <literal>{</literal>;
       when followed by a digit, it is the beginning of a
       <replaceable>bound</replaceable> (see below) </entry>
       </row>

       <row>
       <entry> <replaceable>x</replaceable> </entry>
       <entry> where <replaceable>x</replaceable> is a single character with no other
       significance, matches that character </entry>
       </row>
      </tbody>
     </tgroup>
    </table>

   <para>
    An RE cannot end with a backslash (<literal>\</literal>).
   </para>

   <note>
    <para>
     If you have <xref linkend="guc-standard-conforming-strings"/> turned off,
     any backslashes you write in literal string constants will need to be
     doubled.  See <xref linkend="sql-syntax-strings"/> for more information.
    </para>
   </note>

   <table id="posix-quantifiers-table">
    <title>Regular Expression Quantifiers</title>

    <tgroup cols="2">
     <thead>
      <row>
       <entry>Quantifier</entry>
       <entry>Matches</entry>
      </row>
     </thead>

      <tbody>
       <row>
       <entry> <literal>*</literal> </entry>
       <entry> a sequence of 0 or more matches of the atom </entry>
       </row>

       <row>
       <entry> <literal>+</literal> </entry>
       <entry> a sequence of 1 or more matches of the atom </entry>
       </row>

       <row>
       <entry> <literal>?</literal> </entry>
       <entry> a sequence of 0 or 1 matches of the atom </entry>
       </row>

       <row>
       <entry> <literal>{</literal><replaceable>m</replaceable><literal>}</literal> </entry>
       <entry> a sequence of exactly <replaceable>m</replaceable> matches of the atom </entry>
       </row>

       <row>
       <entry> <literal>{</literal><replaceable>m</replaceable><literal>,}</literal> </entry>
       <entry> a sequence of <replaceable>m</replaceable> or more matches of the atom </entry>
       </row>

       <row>
       <entry>
       <literal>{</literal><replaceable>m</replaceable><literal>,</literal><replaceable>n</replaceable><literal>}</literal> </entry>
       <entry> a sequence of <replaceable>m</replaceable> through <replaceable>n</replaceable>
       (inclusive) matches of the atom; <replaceable>m</replaceable> cannot exceed
       <replaceable>n</replaceable> </entry>
       </row>

       <row>
       <entry> <literal>*?</literal> </entry>
       <entry> non-greedy version of <literal>*</literal> </entry>
       </row>

       <row>
       <entry> <literal>+?</literal> </entry>
       <entry> non-greedy version of <literal>+</literal> </entry>
       </row>

       <row>
       <entry> <literal>??</literal> </entry>
       <entry> non-greedy version of <literal>?</literal> </entry>
       </row>

       <row>
       <entry> <literal>{</literal><replaceable>m</replaceable><literal>}?</literal> </entry>
       <entry> non-greedy version of <literal>{</literal><replaceable>m</replaceable><literal>}</literal> </entry>
       </row>

       <row>
       <entry> <literal>{</literal><replaceable>m</replaceable><literal>,}?</literal> </entry>
       <entry> non-greedy version of <literal>{</literal><replaceable>m</replaceable><literal>,}</literal> </entry>
       </row>

       <row>
       <entry>
       <literal>{</literal><replaceable>m</replaceable><literal>,</literal><replaceable>n</replaceable><literal>}?</literal> </entry>
       <entry> non-greedy version of <literal>{</literal><replaceable>m</replaceable><literal>,</literal><replaceable>n</replaceable><literal>}</literal> </entry>
       </row>
      </tbody>
     </tgroup>
    </table>

   <para>
    The forms using <literal>{</literal><replaceable>...</replaceable><literal>}</literal>
    are known as <firstterm>bounds</firstterm>.
    The numbers <replaceable>m</replaceable> and <replaceable>n</replaceable>