diff --git a/doc/src/sgml/func.sgml b/doc/src/sgml/func.sgml
new file mode 100644
index 0b6a109..2f307c2
*** a/doc/src/sgml/func.sgml
--- b/doc/src/sgml/func.sgml
*************** SELECT ... WHERE CASE WHEN x <> 0 
*** 10015,10020 ****
--- 10015,10022 ----
  <programlisting>
  SELECT COALESCE(description, short_description, '(none)') ...
  </programlisting>
+    This returns <varname>description</> if it is not null, or
+    <varname>short_description</> if it is not null, or <literal>(none)</>.
    </para>
  
     <para>