postgresql7.1
select dotlrn_member_rels_approved.rel_id,
dotlrn_member_rels_approved.rel_type,
dotlrn_member_rels_approved.role,
dotlrn_member_rels_approved.user_id,
registered_users.first_names,
registered_users.last_name,
registered_users.email
from registered_users,
dotlrn_member_rels_approved
where dotlrn_member_rels_approved.community_id = :community_id
and dotlrn_member_rels_approved.user_id = registered_users.user_id
order by (
CASE
WHEN role = 'instructor'
THEN 1
WHEN role = 'admin'
THEN 2
WHEN role = 'teaching_assistant'
THEN 3
WHEN role = 'course_assistant'
THEN 4
WHEN role = 'student'
THEN 6
WHEN role = 'member'
THEN 7
END
) asc, $order_by