如何获取数据透视表中列的平均值

Question

我刚刚学习了数据透视表的概念，有人帮我想出了这个代码来创建一个：（我添加了平均代码）

  SELECT  pvt.Fname,
            pvt.Lname,
            pvt.[English], 
            pvt.[Mathematics], 
            pvt.[Geography], 
            pvt.[Literature], 
            pvt.[French],
            TotalScore = ISNULL(pvt.[English], 0) + ISNULL(pvt.[Mathematics], 0) + ISNULL(pvt.[Geography], 0) + ISNULL(pvt.[Literature], 0) + ISNULL(pvt.[French], 0)

            AverageScore=AVG((pvt.[English]) + (pvt.[Mathematics]) + (pvt.[Geography]) +(pvt.[Literature])+(pvt.[French]))

    FROM    (   SELECT  s.SubjectName, er.Result, su.Fname, su.Lname 
                FROM    Subject AS s
                        INNER JOIN ExamResults AS er
                            ON s.SubjectID = er.SubjectID
                        INNER JOIN Exam AS e
                            ON er.ExamID = e.ExamID
                        LEFT JOIN Student AS su
                            ON er.StudentID = su.StudentID
                WHERE   e.Class = @Class
            ) AS e
            PIVOT 
            (   MAX([Result])
                FOR [SubjectName] IN ([English], [Mathematics], [Geography], [Literature], [French])
            ) AS pvt;




 Fname  |   Lname  | English | Mathematics | Geography | Literature | French | TotalScore| AverageScore
     -------+----------+---------+-------------+-----------+------------+--------+-------------
    Earnest |   Baker  |   100   |     35      |      -    |     -      |   75   |     210    
     House  | Richards |    56   |      -      |     35    |     -      |   75   |     166
     Jacob  |    Jake  |    86   |     37      |      -    |     75     |    -   |     198 

四个表及其列如下：

主题表列：SubjectID,SubjectName

学生表列：StudentID,Fname,Lname

考试表格列：ExamID,ExamDate,ExamPeriod,Class

ExamResults 列：ExamResultID,ExamID,StudentID,SubjectID,Result

问题是，Average 列没有返回任何值。我正在使用 sql 服务器。请你能帮我找出我做错了什么吗？

Answer 1

我建议你在Pivot源查询中找到results的total和average

SELECT pvt.Fname,
       pvt.Lname,
       pvt.[English],
       pvt.[Mathematics],
       pvt.[Geography],
       pvt.[Literature],
       pvt.[French],
       TotalScore,
       AverageScore
FROM   (SELECT s.SubjectName,
               er.Result,
               su.Fname,
               su.Lname,
               TotalScore = Sum(Result)OVER(partition BY Fname, Lname),
                AverageScore = Avg(Result)OVER(partition BY Fname, Lname)
               //AverageScore = Sum(Result)OVER(partition BY Fname, Lname)/5 If you want average for all the subjects
        FROM   Subject AS s
               INNER JOIN ExamResults AS er
                       ON s.SubjectID = er.SubjectID
               INNER JOIN Exam AS e
                       ON er.ExamID = e.ExamID
               LEFT JOIN Student AS su
                      ON er.StudentID = su.StudentID
        WHERE  e.Class = @Class) AS e
       PIVOT ( Max([Result])
             FOR [SubjectName] IN ([English],
                                   [Mathematics],
                                   [Geography],
                                   [Literature],
                                   [French]) ) AS pvt;