how to create a custom group_by field

I have for a module I created, to maintain member data for a karate club, a custom views_handler_field with as query:

  function query() {
    $this->ensure_my_table();
    $this->add_additional_fields();
    $this->field_alias = $this->table . '_' . $this->field;
    $this->query->add_groupby($this->aliases['vid']);
    
    $join = new views_join();
    $join->construct('clubmember_belt', $this->table_alias, 'vid', 'vid');
    
    $this->belts_table = $this->query->ensure_table('clubmember_belt', $this->relationship, $join);
    $this->query->add_field(NULL, "MIN($this->belts_table.gid)", $this->field_alias);
  }

the reason for this query is to grab, from a related table, the entry where clubmember_belt.gid has the lowest number....

This creates, in views, the following query

SELECT node.nid AS nid,
   clubmember.vid AS clubmember_vid,
   MIN(clubmember_belt.gid) AS clubmember_first_belt
 FROM node node 
 LEFT JOIN clubmember clubmember ON node.vid = clubmember.vid
 LEFT JOIN clubmember_belt clubmember_belt ON clubmember.vid = clubmember_belt.vid
 WHERE (node.status <> 0) AND (node.type in ('clubmember'))
 GROUP BY clubmember_vid, nid, clubmember_first_belt

This query however has an error: Can't group on 'clubmember_first_belt'

This code used to work on an older version of Views2 but since going to the latest version it fails.

I see no way to remove the 'clubmember_first_belt' from the group by list. If I do this manually the query works just fine....

I did a rewrite by adding the clubmember_first_belt via a pre_render function and that works but then I can not get click_sort to work correct.

When I change the code in 'views_plugin_query_default.inc' I can get it to work correct. See patch.