Question

要计算考试的平均分，我需要得到以下结果：

subject1 + subject 2 + subject3 +（主题4,5,6的最佳2分之和）+（主题7,8,9,10,11中最佳2分）

部分科目将为null，因为学生只接受7,8,9,10,11

中的任何3项

每项考试都由ExamDateID

定义

我如何实现这一目标？（我需要结果来填充新表...不是这个问题的范围）

Access 2010

Answer 1

考虑在最终查询中使用三个源查询。请注意，在相同的 ExamDateID 和主题范围内的标记将在计算中总结：

主题1-3的考试成绩（使用条件聚合）

SELECT e.StudentID, e.ExamDateID, 
       SUM(IIF(e.Subject BETWEEN 1 AND 3, e.Marks, NULL)) AS SumMarks123
FROM ExamTable AS e
GROUP BY e.StudentID, e.ExamDateID;

主题4-6考试成绩（最高两名）（使用子查询）

SELECT e.StudentID, e.ExamDateID, SUM(e.Marks) AS SumTop2Marks456
FROM ExamTable AS e
WHERE e.Subject BETWEEN 4 AND 6 
AND  (SELECT Count(*) FROM ExamTable sub
      WHERE sub.StudentID = e.StudentID AND sub.ExamDateID = e.ExamDateID
      AND sub.Subject BETWEEN 4 AND 6 AND sub.Marks >= e.Marks)  <= 2
GROUP BY e.StudentID, e.ExamDateID;

主题的考试成绩7-11（最高的两个）（使用子查询）

SELECT e.StudentID, e.ExamDateID, SUM(e.Marks) AS SumTop2Marks711
FROM ExamTable AS e
WHERE e.Subject BETWEEN 7 AND 11
AND  (SELECT Count(*) FROM ExamTable sub
      WHERE sub.StudentID = e.StudentID AND sub.ExamDateID = e.ExamDateID
      AND sub.Subject BETWEEN 7 AND 11 AND sub.Marks >= e.Marks)  <= 2
GROUP BY e.StudentID, e.ExamDateID;

最终查询

SELECT a.StudentID, a.ExamDateID, 
       (a.SumMarks123 + b.SumTop2Marks456 + c.SumTop2Marks711) As SumScore
FROM (ExamAvgSubj123Q a 
INNER JOIN ExamAvgSubj456Q b 
    ON (a.ExamDateID = b.ExamDateID) AND (a.StudentID = b.StudentID)) 
INNER JOIN ExamAvgSubj711Q c 
    ON (a.ExamDateID = c.ExamDateID) AND (a.StudentID = c.StudentID);

当然没有理由，你不能将所有查询合并为一个，但是看到使用派生表维护时可能有点紧张：

SELECT a.StudentID, a.ExamDateID, 
       (a.SumMarks123 + b.SumTop2Marks456 + c.SumTop2Marks711) As SumScore    
FROM
   ((SELECT e.StudentID, e.ExamDateID, 
            SUM(IIF(e.Subject BETWEEN 1 AND 3, e.Marks, NULL)) AS SumMarks123
    FROM ExamTable AS e
    GROUP BY e.StudentID, e.ExamDateID) a 

INNER JOIN 
  (SELECT e.StudentID, e.ExamDateID, SUM(e.Marks) AS SumTop2Marks456
   FROM ExamTable AS e
   WHERE e.Subject BETWEEN 4 AND 6 
   AND  (SELECT Count(*) FROM ExamTable sub
         WHERE sub.StudentID = e.StudentID AND sub.ExamDateID = e.ExamDateID
         AND sub.Subject BETWEEN 4 AND 6 AND sub.Marks >= e.Marks)  <= 2
   GROUP BY e.StudentID, e.ExamDateID) b 

ON (a.ExamDateID = b.ExamDateID) AND (a.StudentID = b.StudentID)) 

INNER JOIN 
  (SELECT e.StudentID, e.ExamDateID, SUM(e.Marks) AS SumTop2Marks711
   FROM ExamTable AS e
   WHERE e.Subject BETWEEN 7 AND 11
   AND  (SELECT Count(*) FROM ExamTable sub
         WHERE sub.StudentID = e.StudentID AND sub.ExamDateID = e.ExamDateID
         AND sub.Subject BETWEEN 7 AND 11 AND sub.Marks >= e.Marks)  <= 2
   GROUP BY e.StudentID, e.ExamDateID) c 

ON (a.ExamDateID = c.ExamDateID) AND (a.StudentID = c.StudentID);

Answer 2

编辑：添加了最佳两个分数

我建议您在button_click事件中使用VBA。以下是代码的概要。你需要改进它：

dim rs as DAO.recordset
dim db as dao.database
set db = current db
dim qry as string
dim avgScore as double
avgScore = 0
numberOfSubject = 0

dim firstBestScore2in3 as double, firstBestScore2in3 as double
firstBestScore2in3 = 0
secondBestScore2in3 = 0

dim firstBestScore2in5 as double, firstBestScore2in5 as double
firstBestScore2in5 = 0
secondBestScore2in5 = 0

'query your database
qry = _
"SELECT studentID, subject, marks " & _
"FROM exams " & _
"WHERE studentID = " & Me.txtStudentID & " " & _
"ORDER BY stubject;"
set rs = db.opendynaset qry

'Iterate through recordset
Do While Not rs.EOF Then

 Select Case rs!subject
  Case 1 To 3
   avgScore = avgScore + rs!subject
  Case 4 To 6
   if (rs!subject > firstBestScore2in3) then
     firstBestScore2in3 = rs!subject
   elseif (rs!subject > secondBestScore2in3) then
     secondBestScore2in3 = rs!subject
   end if
  Case 7 To 11
   if (rs!subject > firstBestScore2in5) then
     firstBestScore2in5 = rs!subject
   elseif (rs!subject > secondBestScore2in5) then
     secondBestScore2in5 = rs!subject
   end if
 end case

 rs.next
loop

avgScore = avgScore + firstBestScore2in3 + secondBestScore2in3 + firstBestScore2in5 + secondBestScore2in5

avgScore = avgScore / 7

检索最高的两个分数

2 个答案: