Question

I’ve got a possibly ‘classic’ mysql max/group by question
Here is my basic table structure.

id | userid | username | date | score
1 | 1111 | joe | 2012-05-16 | 1000
2 | 2222 | john | 2012-03-17 | 2000
3 | 3333 | jill | 2012-02-11 | 3000
4 | 2222 | john | 2012-12-25 | 5000
5 | 3333 | jill | 2012-04-08 | 4000
6 | 1111 | joe | 2012-06-17 | 1000
7 | 1111 | joe | 2012-01-14 | 500
8 | 2222 | john | 2012-06-29 | 6000
9 | 4444 | bill | 2012-08-08 | 4000

I would like to get each user’s highest score.
Each user should have only one score displayed in the result.

My desired result is
id | userid | username | date | score
8 | 2222 | john | 2012-06-29 | 6000
9 | 4444 | bill | 2012-08-08 | 4000
5 | 3333 | jill | 2012-04-08 | 4000
6 | 1111 | joe | 2012-06-17 | 1000

If the user’s highest score appears more than once (ex id 1&6), the most recent date should be displayed.

This is my current query

select s.*
from scores as s
inner join (
    select userid, max(score) as max_score
    from scores
    group by userid
    ) t on s.userid = t.userid and s.score = t.max_score
order by score DESC, date DESC

Which returns the incorrect result of

id | userid | username | date | score
8 | 2222 | john | 2012-06-29 | 6000
9 | 4444 | bill | 2012-08-08 | 4000
5 | 3333 | jill | 2012-04-08 | 4000
6 | 1111 | joe | 2012-06-17 | 1000
1 | 1111 | joe | 2012-05-16 | 1000

Any suggestions on how to resolve this?

I should also mention that the relationship between userid and username is not one to one.

Answer 1

This should give you the result you are looking for. Since MySql doesn’t have a PARTITION function as SQL SERVER, I used a known work around.

SELECT tmp.id, tmp.userid,tmp.username,tmp.`date`,score FROM
   (SELECT *, IF(@prev<>userid, @rownum := 1, @rownum := @rownum+1 ) AS rank,
           @prev := userid
    FROM scores s0
    JOIN (SELECT @rownum := NULL, @prev := 0) AS r
    ORDER BY s0.userid, s0.score DESC, s0.`date` DESC
   ) AS tmp
WHERE tmp.rank=1
ORDER BY tmp.score DESC, tmp.`date` desc