Max of sum query

Question

I\'m trying to write a query that will list student(s) enrolled with the maximum total credit points.

Here is my query:

    SELECT s.S_ID,
       s.S_LAS         


        

Answer 1

Naughty double posting of the same question! This is the answer I gave to your other posting, same thing still applies here.

I'm pretty sure (no Oracle machine to test this) that your alias is the problem:

sum(q1.CREDITS) Total Credits

Should be

sum(q1.CREDITS) "Total Credits"

And therefore

max( q3.Total Credits)

Should be

max( q3."Total Credits")

Or you could get rid of the space in the alias. But there may be more to it than that, as I say, I've no Oracle machine handy to test that out.

Answer 2

You may want to tackle this by just using the group by and Sum(), and retrieve the result with an order by sum() with limit 1 or more depending on how many students your want.

This would eliminate the outer subquery.

Answer 3

Removing all the "noise" your query become

SELECT s.S_ID, s.S_LAST, s.S_FIRST, s."Total Credits"
FROM
  (SELECT ...
   FROM (...) q1
   JOIN (...) q2
  ) q3
GROUP BY s.S_ID, s.S_LAST, s.S_FIRST, s."Total Credits"
WHERE "Total Credits" = max("Total Credits");

It's easy to see that s is not visible from your main query, also in the WHERE condition you're confronting a detail with an aggregation, that's not possible (at least not that way)

Answer 4

If you build your query one join at a time, you will notice, first, that you don't need any of those inline views. You can do it very simply with one CTE definition and a subquery.

WITH
student AS
( SELECT  1 s_id, 'Jones' s_last, 'Sally' s_first FROM dual UNION ALL
  SELECT  2, 'Smith', 'Pete' FROM dual UNION ALL
  SELECT  3, 'DeThroned', 'Kate' FROM dual
),
enrollment AS
( SELECT  1 s_id, 10 c_sec_id FROM dual UNION ALL
  select  1, 11 FROM dual UNION ALL
  select  2, 11 FROM dual UNION ALL
  SELECT  3, 12 FROM dual
),
course_section AS
( SELECT  10 c_sec_id, 101 course_no FROM dual UNION ALL
  SELECT  11, 102 FROM dual UNION ALL
  SELECT  12, 103 FROM dual
),
course AS
( SELECT  101 course_id, 1 credits FROM dual UNION ALL
  SELECT  102, 2 FROM dual UNION ALL
  SELECT  103, 3 FROM dual
),
StudentCredit AS
( SELECT  s.s_id, s_last, s_first, sum( c.credits ) AS TotalCredits
  FROM    student s
  JOIN    enrollment e
    ON    e.s_id = s.s_id
  JOIN    course_section cs
    ON    cs.c_sec_id = e.c_sec_id
  JOIN    course c
    ON    c.course_id = cs.course_no
  GROUP BY s.s_id, s_last, s_first
)
SELECT  *
FROM    StudentCredit
WHERE   TotalCredits = (
          SELECT  MAX( TotalCredits )
          FROM    StudentCredit
        );

Answer 5

SELECT q3.S_ID,
       q3.S_LAST,
       q3.S_FIRST,
      max( q3.Total Credits)
FROM
  (SELECT q2.S_ID,
          q2.S_LAST,
          q2.S_FIRST,
          sum(q1.CREDITS) Total Credits
   FROM
     (SELECT COURSE_NO,
             CREDITS
      FROM COURSE) q1
   JOIN
     (SELECT s.S_ID,
             s.S_LAST,
             s.S_FIRST,
             cs.COURSE_NO
      FROM STUDENT s
      JOIN ENROLLMENT e ON s.S_ID = e.S_ID
      JOIN COURSE_SECTION cs ON e.C_SEC_ID = cs.C_SEC_ID) q2 ON q1.COURSE_NO = q2.COURSE_NO
   GROUP BY q2.S_ID,
            q2.S_LAST,
            q2.S_FIRST) q3
GROUP BY q3.S_ID,
         q3.S_LAST,
         q3.S_FIRST;