Get user's highest score from a table - mysql

Question

I have a feeling this is a very simple question but maybe i'm having brain fart right now and just can't seem to figure out how to go about it.
I have a MySQL table structure like below
+---------------------------------------------------+
| id | date | score | speed | user_id |
+---------------------------------------------------+
| 1 | 2016-11-17 | 2 | 133291 | 17 |
| 2 | 2016-11-17 | 6 | 82247 | 17 |
| 3 | 2016-11-17 | 6 | 21852 | 17 |
| 4 | 2016-11-17 | 1 | 109338 | 17 |
| 5 | 2016-11-17 | 7 | 64762 | 61 |
| 6 | 2016-11-17 | 8 | 49434 | 61 |
Now i can get a particular user's best performance by doing this
SELECT *
FROM performance
WHERE user_id = 17 AND date = '2016-11-17'
ORDER BY score desc,speed asc LIMIT 1
This should return the row with ID = 3. Now what I want is a single query to run to be able to return that 1 such row for each unique user_id in the table. So the resulting result would be something like this
+---------------------------------------------------+
| id | date | score | speed | user_id |
+---------------------------------------------------+
| 3 | 2016-11-17 | 6 | 21852 | 17 |
| 6 | 2016-11-17 | 8 | 49434 | 61 |
Also further more, can I have another question within this same query that would further sort this eventual resulting table by the same criteria of sort (score desc, speed asc). Thanks

Answer 1

A simple method uses a correlated subquery:
select p.*
from performance p
where p.date = '2016-11-17' and
p.id = (select p2.id
from performance p2
where p2.user_id = p.user_id and p2.date = p.date
order by score desc, speed asc
limit 1
);
This should be able to take advantage of an index on performance(date, user_id, score, speed).

Answer 2

Is easy using variable to emulate row_number() over (partition by Order by)
Explanation:
First create two variables in the subquery.
Order by user_id so when user change the #rn reset to 1
Order by score desc, speed asc so each row will have a row_number, and the one you want always will have rn = 1
#rn := you change #rn for each row
if you have a new user_id then #rn is set to 1
otherwise #rn is set to #rn+1
SQL Fiddle Demo
SELECT `id`, `date`, `score`, `speed`, `user_id`
FROM (
SELECT *,
#rn := if(#user_id = `user_id`,
#rn + 1 ,
if(#user_id := `user_id`,1,1)
) as rn
FROM Table1
CROSS JOIN (SELECT #user_id := 0, #rn := 0) as param
WHERE date = '2016-11-17'
ORDER BY `user_id`, `score` desc, `speed` asc
) T
where T.rn =1
OUTPUT

Answer 3

For mysql
You can try with a double in subselect and group by
select * from performance
where (user_id, score,speed ) in (
SELECT user_id, max_score, max(speed)
FROM performance
WHERE (user_id, score) in (select user_id, max(score) max_score
from performance
group by user_id)
group by user_id, max_score
);