<literal>!~~</literal> and <literal>!~~*</literal> operators that
    represent <function>NOT LIKE</function> and <function>NOT
    ILIKE</function>, respectively.  All of these operators are
    <productname>PostgreSQL</productname>-specific.  You may see these
    operator names in <command>EXPLAIN</command> output and similar
    places, since the parser actually translates <function>LIKE</function>
    et al. to these operators.
   </para>

   <para>
    The phrases <function>LIKE</function>, <function>ILIKE</function>,
    <function>NOT LIKE</function>, and <function>NOT ILIKE</function> are
    generally treated as operators
    in <productname>PostgreSQL</productname> syntax; for example they can
    be used in <replaceable>expression</replaceable>
    <replaceable>operator</replaceable> ANY
    (<replaceable>subquery</replaceable>) constructs, although
    an <literal>ESCAPE</literal> clause cannot be included there.  In some
    obscure cases it may be necessary to use the underlying operator names
    instead.
   </para>

   <para>
    Also see the starts-with operator <literal>^@</literal> and the
    corresponding <function>starts_with()</function> function, which are
    useful in cases where simply matching the beginning of a string is
    needed.
   </para>
  </sect2>


  <sect2 id="functions-similarto-regexp">
   <title><function>SIMILAR TO</function> Regular Expressions</title>

   <indexterm>
    <primary>regular expression</primary>
    <!-- <seealso>pattern matching</seealso> breaks index build -->
   </indexterm>

   <indexterm>
    <primary>SIMILAR TO</primary>
   </indexterm>
   <indexterm>
    <primary>substring</primary>
   </indexterm>

<synopsis>
<replaceable>string</replaceable> SIMILAR TO <replaceable>pattern</replaceable> <optional>ESCAPE <replaceable>escape-character</replaceable></optional>
<replaceable>string</replaceable> NOT SIMILAR TO <replaceable>pattern</replaceable> <optional>ESCAPE <replaceable>escape-character</replaceable></optional>
</synopsis>

   <para>
    The <function>SIMILAR TO</function> operator returns true or
    false depending on whether its pattern matches the given string.
    It is similar to <function>LIKE</function>, except that it
    interprets the pattern using the SQL standard's definition of a
    regular expression.  SQL regular expressions are a curious cross
    between <function>LIKE</function> notation and common (POSIX) regular
    expression notation.
   </para>

   <para>
    Like <function>LIKE</function>, the <function>SIMILAR TO</function>
    operator succeeds only if its pattern matches the entire string;
    this is unlike common regular expression behavior where the pattern
    can match any part of the string.
    Also like
    <function>LIKE</function>, <function>SIMILAR TO</function> uses
    <literal>_</literal> and <literal>%</literal> as wildcard characters denoting
    any single character and any string, respectively (these are
    comparable to <literal>.</literal> and <literal>.*</literal> in POSIX regular
    expressions).
   </para>

   <para>
    In addition to these facilities borrowed from <function>LIKE</function>,
    <function>SIMILAR TO</function> supports these pattern-matching
    metacharacters borrowed from POSIX regular expressions:

   <itemizedlist>
    <listitem>
     <para>
      <literal>|</literal> denotes alternation (either of two alternatives).
     </para>
    </listitem>
    <listitem>
     <para>
      <literal>*</literal> denotes repetition of the previous item zero
      or more times.
     </para>
    </listitem>
    <listitem>
     <para>
      <literal>+</literal> denotes repetition of the previous item one
      or more times.
     </para>
    </listitem>
    <listitem>
     <para>
      <literal>?</literal> denotes repetition of the previous item zero
      or one time.
     </para>
    </listitem>
    <listitem>
     <para>
      <literal>{</literal><replaceable>m</replaceable><literal>}</literal> denotes