postgresql7.1 select count(*) from (select acs_rels.object_id_two from acs_rels, membership_rels where acs_rels.object_id_one = (select acs__magic_object_id('registered_users') from dual) and acs_rels.rel_id = membership_rels.rel_id and acs_rels.object_id_two not in ( select acs_rels.object_id_two from acs_rels, dotlrn_user_types where acs_rels.object_id_one = dotlrn_user_types.group_id)) as foo