Maximum mark in Subject with Staff name - sql

Question

Write a query to display list of staff name, subject name handled, maximum mark scored in that subject. Give an alias to the maximum mark as max_mark. Sort the result based on maximum mark in descending.
This is the schema diagram.
This is the code I have tried.
select distinct
staff_name,
subject_name,
max(value) over (partition by sb.staff_id) as max_mark
from subject sb
inner join staff st
on st.staff_id=sb.staff_id
inner join mark m
on m.subject_id=sb.subject_id
order by max_mark desc;
I was abled to pass one testcase but I could not abled to pass second testcase and I don't know what second testcase is and also I am not getting what I have done wrong in my above code.Is there any way of getting solution for this problem.

Answer 1

It seems that You are looking for the following query:
SELECT
ST.STAFF_NAME,
SB.SUBJECT_NAME,
MAX(M.VALUE) AS MAX_MARK
FROM
STAFF ST
JOIN SUBJECT SB ON SB.STAFF_ID = ST.STAFF_ID
JOIN MARK M ON M.SUBJECT_ID = SB.SUBJECT_ID
GROUP BY
ST.STAFF_ID,
ST.STAFF_NAME,
SB.SUBJECT_ID,
SB.SUBJECT_NAME
ORDER BY
MAX_MARK DESC;

Answer 2

I think that you want aggregation:
select
st.staff_name,
su.subject_name,
max(ma.value) as max_mark
from subject su
inner join staff st on st.staff_id = sb.staff_id
inner join mark ma on ma.subject_id = su.subject_id
group by st.staff_id, st.staff_name, su.subject_id, su.subject_name
order by max_mark desc;

Answer 3

You can use window functions:
select staff_name, subject_name, max_mark
from (select st.staff_name, su.subject_name, ma.value as max_mark,
row_number() over (partition by st.staff_name order by ma.value desc) as seqnum
from subject su join
staff st
on st.staff_id = sb.staff_id join
mark ma
on ma.subject_id = su.subject_id
) s
order by max_mark desc;
You can also use your method (select distinct with window functions) . . . but you have to deal with subject_name:
select distinct staff_name,
first_value(subject_name) over (partition by sb.staff_id order by value desc) as subject_name
max(value) over (partition by sb.staff_id) as max_mark
from subject sb
inner join staff st
on st.staff_id=sb.staff_id
inner join mark m
on m.subject_id=sb.subject_id
order by max_mark desc;