Question

我有以下表格：

Table 1
Student , Exam_ID
1      1      
2      1     
3      2     
1      2     
3      3     
2      3     
3      4     
1      4  

Table 2
Exam ID, Mark
(1   , 5)
(2 ,   4)
(3  ,  4)
(4 ,   5)

Table 3
Exam ID, Teacher's review
(1,3)
(2,5)
(3,4)
(4,2)

Table 4
Exam_ID, Start_Time, End_Time
(1,2:00:00,3:50:00)
(2,2:00:00,4:00:00)
(3,3:00:00,5:20:00)
(4,3:00:00,5:00:00)

每个考试由成对的学生解决...我希望能够对每对学生所进行的所有考试的分数，教师评论进行平均，例如：考试2和4由同一对考试学生（3,1）我希望能够平均那些（4,5）= 4.5和教师评论（5,2）= 3.5的2门考试的分数然后将这些对从最高分到最低分和教师评论进行排名，并能够计算每次考试的开始和结束时间之间的差异，并将其包括在排名中所以所需的表格如下：

StudentA, StudentB, AverageMark, AverageTeacher'sReview, AverageExamDuration
( 3,       1,        4.5,           3.5,                     2:00:00)

等

相关问题：average-multiple-rows-in-a-column-in-access

谢谢

Answer 1

听起来像是家庭作业，第一次加入的！=可能就是你应该学习的东西。

select A.StudentId as StudentA, 
B.StudentId as StudentB,
AVG(Mark) as AvgMark,
AVG(review) as AvgReview, 
AVG(DATEDIFF(MINUTE,StartTime,EndTime)) as AvgTime
from StudentToExam A 
inner join StudentToExam B on A.ExamId = B.ExamId and A.StudentId != B.StudentId
inner join ExamToMark M on A.ExamId = M.ExamId
inner join ExamToReview R on A.ExamId = R.Review
inner join ExamDuration D on D.ExamId = A.ExamId
GROUP BY A.StudentId, B.StudentId

访问sql平均三列

1 个答案: