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

问题

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

回答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:

回答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

回答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``

来源：https://stackoverflow.com/questions/24924591/how-can-i-group-student-scores-into-quintile-using-sql-server-2008