C"><div class="titlepage"><div><div><h2 class="title" style="clear: both">38.3. User-Defined Functions <a href="#XFUNC" class="id_link">#</a></h2></div></div></div><a id="id-1.8.3.6.2" class="indexterm"></a><p>
   <span class="productname">PostgreSQL</span> provides four kinds of
   functions:

   </p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>
      query language functions (functions written in
      <acronym class="acronym">SQL</acronym>) (