PHP SQL查询过滤器

I am working on a website. (CMS e107 version 1.xx)

I am setting up a custom page that will display some user information...

Current SQL query that I've been using:

$result = mysql_query("
SELECT user_armaid AS profile_id
     , user_anickname AS profile_name
     , user_aremark AS profile_remark
     , user_aemail AS email
     , user_aicq AS icq
  FROM db_user_extended
 WHERE user_armaid IS NOT NULL 
   AND user_anickname IS NOT NULL
 ");

That works fine - but right now it will display anything (http://squad.1stcavdiv.us)

What I want it to do is only show the users who are in a certain user group (in e107 it is user class).

I do not know how they query would be like... I was thinking of using something like this:

$query1 = mysql_query("
SELECT user_id
     , user_class 
  FROM db_user 
 WHERE db_user.user_id = db_user_extended.user_extended_id 
   AND (FIND_IN_SET('5', user_class))
");

but I don't really know how to do it. Some help would be nice.