SQL Server 模式 SQL

Question

我有一张表格，列出了每个班级的学生成绩。我想要一个如下所示的结果集：

BIO...B
CHEM...C

其中“B”和“C”是该类的模式。我可以获得所有成绩的模式，但不确定如何获得每个班级的模式

Answer 1

这里，在 SQL 2005/2008 上是这样的：

;WITH 
  Counts AS (
    SELECT ClassName, Grade, COUNT(*) AS GradeFreq 
    FROM Scores
    GROUP BY ClassName, Grade
    )
, Ranked AS (
    SELECT ClassName, Grade, GradeFreq
    , Ranking = DENSE_RANK() OVER (PARTITION BY ClassName ORDER BY GradeFreq DESC)
    FROM Counts
    )
SELECT * FROM Ranked WHERE Ranking = 1

或者也许只是：

;WITH Ranked AS (
  SELECT 
    ClassName, Grade
  , GradeFreq = COUNT(*)
  , Ranking = DENSE_RANK() OVER (PARTITION BY ClassName ORDER BY COUNT(*) DESC)
  FROM Scores
  GROUP BY ClassName, Grade
  )
SELECT * FROM Ranked WHERE Ranking = 1