Find MIN value based on two columns in MySQL - mysql

Question

I've table in MySQL with athletic performs.
Structure:
id (PRIMARY KEY)
athlete_id (FOREIGN KEY)
perform
category_id
discipline_id
If I want to select the best performs from this table (each athlete can be in results max once), I use this query:
SELECT
*
FROM
performs NATURAL
JOIN athletes
JOIN
(SELECT
athlete_id,
MIN(perform) AS perform,
category_id,
discipline_id
FROM
zaznamy
WHERE discipline_id = 4
AND category_id = 3
GROUP BY athlete_id) rec
ON performs.athlete_id = rec.athlete_id
AND performs.perform = rec.perform
AND performs.category_id = rec.category_id
AND performs.discipline_id = rec.discipline_id
ORDER BY performs.perform
LIMIT 25
I get right results. But I want to select the best performs from one discipline and more category together (e.g. Mens with Juniors etc). How do I use clause GROUP BY for two columns?

Answer 1

Maybe I don't understand something, but you can add two columns in group by, like the following example. Just add ,(comma) between the two or more columns.
SELECT
*
FROM
performs NATURAL
JOIN athletes
JOIN
(SELECT
athlete_id,
MIN(perform) AS perform,
category_id,
discipline_id
FROM
zaznamy
WHERE discipline_id = 4
GROUP BY athlete_id,category_id) rec
ON performs.athlete_id = rec.athlete_id
AND performs.perform = rec.perform
AND performs.category_id = rec.category_id
AND performs.discipline_id = rec.discipline_id
ORDER BY performs.perform
LIMIT 25 enter code here
EDIT - UPDATE
Ok, now I understand your problem. This is quite common, actually, where you want first to find the max value of a group and then request additional info on that value.
One way to achieve this is with a nested query as follow
SELECT ss.athlete_id,ss.perform,category_id
FROM performs ss
inner join
(SELECT
athlete_id, MIN(perform) AS perform
FROM
performs
WHERE
discipline_id = 4 AND category_id IN (1,3,5,7,9)
GROUP BY
athlete_id) tt
on tt.athlete_id = ss.athlete_id and ss.perform = tt.perform
The result is the one you described above.

Answer 2

If I use this query:
SELECT
athlete_id, MIN(perform) AS perform, category_id
FROM
performs
WHERE
discipline_id = 4 AND category_id IN (1,3,5,7,9)
GROUP BY
athlete_id, category_id
I get this results:
athlete_id perform category_id
1 11,14 1
1 11,54 3
1 11,54 5
1 10,71 7
2 11,04 1
2 11,24 3
2 11,54 5
2 12,14 7
3 10,94 1
4 10,94 1
4 11,34 3
But I need this result:
athlete_id perform category_id
1 10,71 7
2 11,04 1
3 10,94 1
4 10,94 1
For each athlete_id the best perform at once category_id.
This result will be JOIN with full table "perform".

Answer 3

SQL:
SELECT ss.athlete_id,ss.perform,category_id
FROM performs ss
INNER JOIN
(SELECT
athlete_id, MIN(perform) AS perform
FROM
performs
WHERE
discipline_id = 4 AND category_id IN (1,3,5,7,9)
GROUP BY
athlete_id) tt
ON tt.athlete_id = ss.athlete_id and ss.perform = tt.perform
Results:
athlete_id perform category_id
1 7,04 1
2 7,14 1
3 7,14 1
4 7,24 1
5 7,14 1
6 7,24 1
6 7,24 3
7 7,02 1
8 7,07 1
9 7,34 1
10 7,34 1
11 7,18 1
12 7,04 3
13 7,44 1
13 7,44 5
14 7,44 1
15 7,27 1
I´ve tried clause DISTINCT but results were same.