CODEWITHSUNDEEP
sql-serversql-server-2008greatest-n-per-group
Jainendra
Jainendra

Reputation: 25153

How to select records with parent child relation having maximum score for a parent

I have tables in like this:

ExerciseAttempt(attemptId, ExerciseId, Score, studentId)
ExerciseMeta(ExerciseId, ParentId)

Each exercise has one parent. A parent can have many child exercises. Now I want to find the records such that only one child of a parent(the one with max score) is considered.

For example:

ExericeAttempt:

attemptId | ExerciseId | Score | studentId
1         | 10         |  18   | 10001
2         | 11         |  12   | 10001
3         | 12         |  20   | 10001
4         | 13         |  22   | 10001
5         | 13         |  21   | 10001

ExerciseMeta:

ExerciseId | ParentId
10         |  100
11         |  100
12         |  101
13         |  101

For these tables the result should be

attemptId | ExerciseId | Score | studentId
1         | 10         |  18   | 10001
4         | 13         |  22   | 10001

Also multiple attempts of a same exercise are possible. How can I achieve this in SQL SERVER?

Upvotes: 0

Views: 169

Answers (1)

dean
dean

Reputation: 10098

 ;with x as (
    select ea.*, em.parentid,
    row_number() over(partition by parentid order by score desc) as rn
    from ExericeAttempt ea
    inner join ExerciseMeta em
    on ea.ExerciseId = em.ExerciseId
)
select attemptId, ExerciseId, Score, studentId
from x
where rn = 1

Result:

ATTEMPTID   EXERCISEID  SCORE   STUDENTID
1           10          18      10001
4           13          22      10001

Result in Fiddle.

Upvotes: 2

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