<replaceable>pattern</replaceable> <optional>ESCAPE <replaceable>escape-character</replaceable></optional>
</synopsis>

    <para>
     The <function>LIKE</function> expression returns true if the
     <replaceable>string</replaceable> matches the supplied
     <replaceable>pattern</replaceable>.  (As
     expected, the <function>NOT LIKE</function> expression returns
     false if <function>LIKE</function> returns true, and vice versa.
     An equivalent expression is
     <literal>NOT (<replaceable>string</replaceable> LIKE
      <replaceable>pattern</replaceable>)</literal>.)
    </para>

    <para>
     If <replaceable>pattern</replaceable> does not contain percent
     signs or underscores, then the pattern only represents the string
     itself; in that case <function>LIKE</function> acts like the
     equals operator.  An underscore (<literal>_</literal>) in
     <replaceable>pattern</replaceable> stands for (matches) any single
     character; a percent sign (<literal>%</literal>) matches any sequence
     of zero or more characters.
    </para>

   <para>
    Some examples:
<programlisting>
'abc' LIKE 'abc'    <lineannotation>true</lineannotation>
'abc' LIKE 'a%'     <lineannotation>true</lineannotation>
'abc' LIKE '_b_'    <lineannotation>true</lineannotation>
'abc' LIKE 'c'      <lineannotation>false</lineannotation>
</programlisting>
   </para>

   <para>
    <function>LIKE</function> pattern matching supports nondeterministic
    collations (see <xref linkend="collation-nondeterministic"/>), such as
    case-insensitive collations or collations that, say, ignore punctuation.
    So with a case-insensitive collation, one could have:
<programlisting>
'AbC' LIKE 'abc' COLLATE case_insensitive    <lineannotation>true</lineannotation>
'AbC' LIKE 'a%' COLLATE case_insensitive     <lineannotation>true</lineannotation>
</programlisting>
    With collations that ignore certain characters or in general that consider
    strings of different lengths equal, the semantics can become a bit more
    complicated.  Consider these examples:
<programlisting>
'.foo.' LIKE 'foo' COLLATE ign_punct    <lineannotation>true</lineannotation>
'.foo.' LIKE 'f_o' COLLATE ign_punct    <lineannotation>true</lineannotation>
'.foo.' LIKE '_oo' COLLATE ign_punct    <lineannotation>false</lineannotation>
</programlisting>
    The way the matching works is that the pattern is partitioned into
    sequences of wildcards and non-wildcard strings (wildcards being
    <literal>_</literal> and <literal>%</literal>).  For example, the pattern
    <literal>f_o</literal> is partitioned into <literal>f, _, o</literal>, the
    pattern <literal>_oo</literal> is partitioned into <literal>_,
    oo</literal>.  The input string matches the pattern if it can be
    partitioned in such a way that the wildcards match one character or any
    number of characters respectively and the non-wildcard partitions are
    equal under the applicable collation.  So for example, <literal>'.foo.'
    LIKE 'f_o' COLLATE ign_punct</literal> is true because one can partition
    <literal>.foo.</literal> into <literal>.f, o, o.</literal>, and then
    <literal>'.f' = 'f' COLLATE ign_punct</literal>, <literal>'o'</literal>
    matches the <literal>_</literal> wildcard, and <literal>'o.' = 'o' COLLATE
    ign_punct</literal>.  But <literal>'.foo.' LIKE '_oo' COLLATE
    ign_punct</literal> is false because <literal>.foo.</literal> cannot be
    partitioned in a way that the first character is any character and the
    rest of the string compares equal to <literal>oo</literal>.  (Note that
    the single-character wildcard always matches exactly one character,
    independent of the collation.  So in this example, the
    <literal>_</literal> would match <literal>.</literal>, but then the rest
    of the input string won't match the rest of the pattern.)
   </para>

   <para>
    <function>LIKE</function> pattern matching always covers the entire
    string.  Therefore, if it's desired