Question

Just wondering what’s a better way to write this query. Cheers.

SELECT r.user_id AS ID, m.prenom, m.nom
FROM `0_rank` AS l
LEFT JOIN `0_right` AS r ON r.rank_id = l.id
LEFT JOIN `0_user` AS m ON r.user_id = m.id
WHERE r.section_id = $section_id
AND l.rank = '$rank_name' AND depart_id IN 
(SELECT depart_id FROM 0_depart WHERE user_id = $user_id AND section_id = $section_id) 
GROUP BY r.user_id

Here are the table structures:

• 0_rank: id | section_id | rank_name |
  other_stuffs
• 0_user: id | prenom | nom | other_stuffs
• 0_right: id | section_id | user_id |
  rank_id | other_stuffs
• 0_depart: id | section_id | user_id | depart_id
  | other_stuffs

The idea is to use the same in a function like:

public function usergroup($section_id,$rank_name,$user_id) { 
 // mysql query goes here to get a list of appropriate users
}

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Update: I think I have not been able to express myself clearly earlier. Here is the most recent query that seems to be working.

SELECT m.id, m.prenom, m.nom, 
CAST( GROUP_CONCAT( DISTINCT d.depart ) AS char ) AS deps, 
CAST( GROUP_CONCAT( DISTINCT x.depart ) AS char ) AS depx
FROM `0_rank` AS l
LEFT JOIN `0_right` AS r ON r.rank_id = l.id
LEFT JOIN `0_member` AS m ON r.user_id = m.id
LEFT JOIN `0_depart` AS d ON m.id = d.user_id
LEFT JOIN `0_depart` AS x ON x.user_id = $user_id
WHERE r.section = $section_id
AND l.rank = '$rank_name'
GROUP BY r.user_id ORDER BY prenom, nom

Now I want to get only those result, where all entries of deps are present in entries in depx.

In other term, every user is associated with some departs. $user_id is also an user is associated with some departs.

I want to get those users whose departs are common to the departs of $user_id.

Cheers.

Answer 1

Update

I’m not sure without being able to see the data but I believe this query will give you the results you want the fastest.

SELECT m.id, m.prenom, m.nom, 
CAST( GROUP_CONCAT( DISTINCT d.depart ) AS char ) AS deps, 
FROM `0_rank` AS l
LEFT JOIN `0_right` AS r ON r.rank_id = l.id and r.user_id = $user_id
LEFT JOIN `0_member` AS m ON r.user_id = m.id
LEFT JOIN `0_depart` AS d ON m.id = d.user_id
WHERE r.section = $section_id
AND l.rank = '$rank_name'
GROUP BY r.user_id ORDER BY prenom, nom

Let me know if this works.

---

Try this:
(By converting the functionality of the IN (SELECT…) to an inner join, you get exactly the same results but it might be the optimizer will make better choices.)

SELECT r.user_id AS ID, m.prenom, m.nom
FROM `0_rank` AS l
LEFT JOIN `0_right` AS r ON r.rank_id = l.id and r.section_id = 2
LEFT JOIN `0_user` AS m ON r.user_id = m.id
INNER JOIN `0_depart` AS x ON l.section_id = x.section_id and x.user_id = $user_id AND x.section_id = $section_id
WHERE l.rank = 'mod' 
GROUP BY r.user_id

I also moved the constraints on 0_right to the join statement because I think that is clearer — presumably this change won’t matter to the optimizer.