MS Access Select top n query grouped by multiple fields

This is part 2 of a problem that was already answered by peterm on this board. Thanks again peterm!

So I have code that will return the top 3 test scores for a given student. My table looks like the following:

StudentID, Test ID, Score
1,1, 95
1, 2, 90
1, 3, 90
1, 4, 90
2, 1, 99
2, 2, 95
2, 3, 90
2, 4, 90

Thanks to peterm, I have the following code which will do this for me:

SELECT StudentID, TestID, TestScore
  FROM MyTable t
 WHERE TestID IN
(
  SELECT TOP 3 TestID 
    FROM MyTable
   WHERE StudentID = t.StudentID 
   ORDER BY TestScore DESC, TestID
)
 ORDER BY StudentID, TestScore DESC, TestID;

My new problem is now I need to add two new fields to the table for Subject and Year, so I need to find the top 3 scores for each Subject-Student-Year combination. Once I have the top 3 scores for each combination, I need to average them so that I will have one averaged score of the top 3 scores for each student-subject-year combination. Hopefully, I’ve explained this clearly enough without having to mock up another table.

Thanks in advance.

Answer

You can do something like this

SELECT StudentID, Year, Subject,  AVG(TestScore) AS AvgScore
  FROM
(
  SELECT StudentID, Year, Subject, TestScore
   FROM MyTable t
   WHERE TestID IN
  (
   SELECT TOP 3 TestID 
     FROM MyTable
    WHERE StudentID = t.StudentID
      AND Year = t.Year
      AND Subject = t.Subject
    ORDER BY TestScore DESC, TestID
  )
) q
 GROUP BY StudentID, Year, Subject
 ORDER BY StudentID, Year, Subject;

Sample output:

| STUDENTID | YEAR | SUBJECT | AVGSCORE |
|-----------|------|---------|----------|
|         1 | 2012 |       1 |       91 |
|         1 | 2012 |       2 |       84 |
|         2 | 2012 |       1 |       94 |
|         2 | 2012 |       3 |       95 |

Here is SQLFiddle demo.
Demo as usually is for SQL Server but expected to work in MS Access, maybe with minor syntactic tweaks