获取子计数以及平均值和计数

Question

我有两张桌子...

MODULES                ENROLMENTS
GroupNo                StudentNo
Title                  GroupNo
Tutor                  CourseworkMark
DayNo                  ExamMark
Time
Room
Semester

我想创建一个视图，显示每个模块在课程作业和考试中取得的平均分数，以及达到 >70、60-69、50-59、40-49 和<40。这可能吗？

我用...计算了平均分

SELECT Title,
       AVG(CourseworkMark) AS AverageCoursework,
       AVG(ExamMark) AS AverageExam
FROM tblModules INNER JOIN tblEnrolments
   ON tblModules.GroupNo = tblEnrolments.GroupNo
GROUP BY Title;

Answer 1

您可以使用 SUMmed CASE 表达式来执行此操作；

SELECT Title,
       AVG(CourseworkMark) AS AverageCoursework,
       AVG(ExamMark) AS AverageExam,
       SUM(CASE WHEN CourseworkMark > 70 THEN 1 ELSE 0 END) AS CourseworkMarkOver70,
       SUM(CASE WHEN CourseworkMark BETWEEN 60 AND 70 THEN 1 ELSE 0 END) AS CourseworkMarkOver60To69,
       SUM(CASE WHEN CourseworkMark BETWEEN 50 and 59 THEN 1 ELSE 0 END) AS CourseworkMarkOver50To59,
       SUM(CASE WHEN CourseworkMark BETWEEN 40 and 49 THEN 1 ELSE 0 END) AS CourseworkMarkOver40To49,
       SUM(CASE WHEN CourseworkMark < 40 THEN 1 ELSE 0 END) AS CourseworkMarkUnder40
FROM tblModules INNER JOIN tblEnrolments
   ON tblModules.GroupNo = tblEnrolments.GroupNo
GROUP BY Title;

获取子计数以及平均值和计数

Getting sub-counts along with Average and Count

sql

sql-server

count

average