Left registration, ordering, MySQL optimization

Question

I have a query like this:

   SELECT m...., a...., r....
     FROM 0_member AS m                 
LEFT JOIN 0_area AS a ON a.user_id = (SELECT user_id 
                                        FROM `0_area` 
                                       WHERE user_id = m.id 
                                    ORDER BY sec_id ASC LIMIT 1)
LEFT JOIN 0_rank as r ON a.rank_id = r.id 
    WHERE m.login_userid = '$username'

The idea is to get the first row from table 0_area and, therefore, try an internal join. However, it does not work as expected.

Between 0_area and 0_member, 0_member.id = 0_area.user_id. However, there are several lines 0_area.user_id, and I want the line to have the lowest sec_id value.

Any help please?

Answer 1

   SELECT m...., a...., r....
     FROM 0_member AS m               
LEFT JOIN (SELECT user_id, min(sec_id) minsec
           FROM `0_area`
           GROUP BY user_id) g1 on g1.user_id=m.id
LEFT JOIN 0_area AS a ON a.user_id = g1.user_id and a.sec_id=minsec
LEFT JOIN 0_rank as r ON a.rank_id = r.id 
    WHERE m.login_userid = '$username'