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Postgres documentation

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<para>

Note that the backslash already has a special meaning in string

literals, so to write a pattern constant that contains a backslash

you must write two backslashes in the query. You can avoid this by

selecting a different escape character with <literal>ESCAPE</literal>.

you must write two backslashes in the query. Thus, writing a pattern

that actually matches a literal backslash means writing four backslashes

in the query. You can avoid this by selecting a different escape

character with <literal>ESCAPE</literal>; then backslash isn't special

to <function>LIKE</> anymore. (But it's still special to the string

literal parser, so you still need two of them.)

</para>

<para>

It's also possible to select no escape character by writing

<literal>ESCAPE ''</literal>. In this case there is no way to

turn off the special meaning of underscore and percent signs in

the pattern.

</para>

<para>

<function>ILIKE</function>. There are also

<literal>!~~</literal> and <literal>!~~*</literal> operators that

represent <function>NOT LIKE</function> and <function>NOT

ILIKE</function>. All of theseare also

ILIKE</function>. All of theseoperators are

<productname>Postgres</productname>-specific.

</para>

</sect2>