How to select the 16 highest values out of 18 values SQL?

Ok so I have changed it from columns to rows instead 😉

Im saving grades for students. I have a MySQL table called “grade” with three columns called “subject”, “points” and “userId” with 18 rows with different subjects where each subject can have one of the values 20, 17.5, 15 or 12.5

So all users have the same “subjects” but can have different “points”

"subject"            "points"   "userId"

svenska              20          23
engelska             15          23
bild                 12.5        23
biologi              15          23
matte                17.5        23
fysik                20          23
historia             12.5        23
hemkunskap           15          23
kemi                 17.5        23
historia             20          23
idrott               12.5        23
moderanspråk         15          23
modersmål            17.5        23
musik                12.5        23
religion             20          23
samhällskunskap      15          23
slöjd                12.5        23
teknik               17.5        23

I need to select and sum the values from the 16 “subjects” that have the highest values out of the 18 “subjects”.

How do I do that? Any input really appreciated, thanks.

Answer

You can use a subquery to get 16 rows with the most points:

select sum(points)
from (select g.*
      from grades g
      order by points desc
      limit 16
     ) g;

If you want this per user, you would use window functions:

select userid, sum(points)
from (select g.*,
             row_number() over (partition by userid order by points desc) as seqnum
      from grades g
     ) g
where seqnum <= 16
group by userid