MySQL : Get max values of groups - mysql

Question

I have a table:
user_id | fav_song_genre | votes_as_fav_member
--------+----------------+--------------------
1 | hip hop | 3
2 | hip hop | 5
3 | rock | 8
4 | rock | 6
How do I get only results of user_id's with the highest votes_as_fav_member per group fav_song_genre:
Something like
SELECT *, MAX(votes_as_fav_member) as most_votes
FROM table
GROUP BY
fav_song_genre
I'm using that but it's not giving me the ID's of the members with most votes per genre.

Answer 1

This is not a problem of MySQL, rather a bit of logic problem with your approach.
Let's say we have the following:
user_id | fav_song_genre | votes_as_fav_member
--------+----------------+--------------------
1 | hip hop | 3
2 | hip hop | 5
3 | rock | 8
4 | rock | 6
5 | hip hop | 5
6 | rock | 8
Which ID should the query return? Should it return only one? or all that have the same amount of votes?
So, if you require only a single ID, what is the differentiation of a draw?
Lieven beat me to the SQL resolution by a few seconds, though.

Answer 2

Reasoning goes like
SELECT max vote for each genre
JOIN back with the original table to retrieve the additional columns for the records found.
SQL Statement
SELECT us.*
FROM UserSongs us
INNER JOIN (
SELECT fav_song_genre
, MAX(votes_as_fav_member) AS votes_as_fav_member
FROM UserSongs
GROUP BY
fav_song_genre
) usm ON usm.fav_song_genre = us.fav_song_genre
AND usm.votes_as_fav_member = us.votes_as_fav_member
Edit
How can I make sure the person with the lower ID is returned
SELECT MIN(us.user_id) as user_id
, us.fav_song_genre
, us.votes_as_fav_member
FROM UserSongs us
INNER JOIN (
SELECT fav_song_genre
, MAX(votes_as_fav_member) AS votes_as_fav_member
FROM UserSongs
GROUP BY
fav_song_genre
) usm ON usm.fav_song_genre = us.fav_song_genre
AND usm.votes_as_fav_member = us.votes_as_fav_member
GROUP BY
us.fav_song_genre
, votes_as_fav_member

Answer 3

Not sure if that's what you are asking:
SELECT g.fav_song_genre
, t.user_id
, g.most_votes
FROM yourTable t
JOIN
( SELECT fav_song_genre
, MAX(votes_as_fav_member) as most_votes
FROM yourTable
GROUP BY fav_song_genre
) AS g
ON t.fav_song_genre = g.fav_song_genre
AND t.votes_as_fav_member= g.most_votes
;

Answer 4

I created the table and tested, and I think this will also work
Table Data:
user_id fav_song_genre votes_as_fav_member
1 hip_hop 3
2 hip_hop 5
3 rock 8
4 rock 6
5 blues 20
6 indie 18
7 rock 35
8 country 33
9 hip_hop 35
10 indie 5
11 blues 7
12 hip_hop 59
13 indie 187
14 classic 45
15 country 61
16 hip_hop 243
Query:
select t.user_id, t.fav_song_genre, t.votes_as_fav_member
from (
select user_id, max(votes_as_fav_member) as max_votes, fav_song_genre
from table1 group by fav_song_genre
)
as x inner join table1 as t on t.votes_as_fav_member = x.max_votes and t.fav_song_genre = x.fav_song_genre;
Results:
user_id fav_song_genre votes_as_fav_member
5 blues 20
7 rock 35
13 indie 187
14 classic 45
15 country 61
16 hip_hop 243