CODEWITHSUNDEEP
sqlsql-server-2008greatest-n-per-group
Bonn
Bonn

Reputation: 63

SQL Get rows based on max column

I have problem getting row from a max column, here the illustration : http://sqlfiddle.com/#!3/15207/9

basically I want to get the student's highest grade along with the grade-id (gid). but the query is not right because of using max grade id which will return 2.

First course taken, the student got D (1 point). Second time course taken, the student got E (0 point).

The gradeid for that 1 point is 1.

I expect the query result is: 1 (userid), 1 (subjectid), 1 (gradeid), 1 (score)

Thanks

UPDATE 01:

The more improved example: http://sqlfiddle.com/#!3/97997/2

Upvotes: 1

Views: 227

Answers (1)

John Woo
John Woo

Reputation: 263893

UPDATE 1

WITH highestScore
AS
(
    SELECT  a.uid StudentID,
            a.uname StudentName,
            b.Score, 
            c.cname CourseName,
            c.semester,
            d.sname SubjectName, d.sid, 
            DENSE_RANK() OVER (PARTITION BY a.uid, d.sid
                               ORDER BY b.Score DESC) rn
    FROM    Users a
            INNER JOIN Grades b
                ON a.uid = b.uid
            INNER JOIN Courses c
                ON b.cid = c.cid
            INNER JOIN Subjects d
                ON c.sid = d.sid
)
SELECT  StudentID, StudentName, CourseName, semester,
        SubjectName, Score
FROM    highestScore
WHERE   StudentID = 1 AND  -- StudentID
        sid = 1 AND        -- SubjectID
        RN = 1             -- leave this as is (rank of the highest score)

Upvotes: 3

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