How can I group student scores into quintile using SQL Server 2008

Question

Can anyone help me to group student scores into quintile? I think there is a feature in SQL Server 2012, but still we havent upgraded to it as we are using 2008R2. I triedNtile(5)` but it is not generating the desired result. I need below Quintile column

Student   Score Quintile ------------------------     Student1     20   1 Student2     20   1 Student3     30   2 Student4     30   2 Student5     40   2 Student6     40   2 Student7     50   3 Student8     50   3 Student9     60   3 Student10    70   4 Student11    70   4 Student12    80   4 Student13    80   4 Student14    90   5 

Answer 1

You must have been doing something wrong when using NTILE(5) - that IS the function to use!

Here's my test setup:

DECLARE @Students TABLE (StudentID INT IDENTITY(1,1), StudentName VARCHAR(20), Score INT)  INSERT INTO @Students(StudentName, Score) VALUES ('Student 1', 20), ('Student 2', 20),  ('Student 3', 30), ('Student 4', 30),  ('Student 5', 40), ('Student 6', 40),  ('Student 7', 50), ('Student 8', 50),  ('Student 9', 60),  ('Student 10', 70), ('Student 11', 70),  ('Student 12', 80), ('Student 13', 80),  ('Student 14', 90)   SELECT      StudentName, Score,      Quintile = NTILE(5) OVER(ORDER BY Score) FROM         @Students 

And the output is:

Answer 2

Borrowed from marc_s +1

DECLARE @Students TABLE (StudentID INT IDENTITY(1,1), StudentName VARCHAR(20), Score INT)  INSERT INTO @Students(StudentName, Score) VALUES ('Student 1', 20), ('Student 2', 20),  ('Student 3', 30), ('Student 4', 30),  ('Student 5', 40), ('Student 6', 40),  ('Student 7', 50), ('Student 8', 50),  ('Student 9', 60), ('Student 10', 70),  ('Student 11', 70),('Student 12', 80),  ('Student 13', 80),('Student 14', 90)  SELECT s.StudentName, s.Score, qm.maxQ   FROM @Students as s   join ( select score, MAX(Quintile) as maxQ            from ( SELECT Score, Quintile = NTILE(5) OVER(ORDER BY Score)                     FROM  @Students ) q            group by q.score ) qm     on qm.Score = s.Score 

Answer 3

Below is the correct answer given by Erland Sommarskog  Create Table #Scores(Student varchar(20), Score int);  Insert #Scores(Student, Score) Values  ('Student1', 20)  ,('Student2', 20)  ,('Student3', 30) ,('Student4', 30) ,('Student4', 30) ,('Student4', 30) ,('Student5', 40) ,('Student6', 40) ,('Student7', 50) ,('Student8', 50) ,('Student9', 60) ,('Student10', 70) ,('Student11', 70)  ,('Student12', 80)  ,('Student13', 80)  ,('Student14', 90);   ; WITH quintiles AS (     SELECT Score, ntile(5) OVER(ORDER BY Score) AS quintile      FROM   (SELECT DISTINCT Score FROM #Scores) AS s  ) SELECT s.Student, s.Score, q.quintile FROM   #Scores s JOIN   quintiles q ON s.Score = q.Score go DROP TABLE #Scores  --by Erland Sommarskog``