我正在mysql 5.0中构建一个查询来计算学生学期成绩。初始表(studentItemGrades)包含将用于计算最终成绩的作业列表等。每项作业都有一个PossibleScore,Grade和Weight。计算应对所有类似加权的项目进行分组,并根据分配到期的日期范围提供SUM(GRADE)/ SUM(POSSIBLESCORE)。我遇到的问题是所有个别加权等级的最终总和。例如,结果目前产生以下结果:
CourseScheduleID sDBID AssignedDate DueDate Weight WeightedGrade
1 519 2010-08-26 2010-08-30 10 0.0783333333333333
1 519 2010-09-01 2010-09-03 20 0.176
1 519 2010-09-01 2010-09-10 70 0.574
来自查询的:
SELECT CourseScheduleID, sDBID, AssignedDate, DueDate, Weight,
((SUM(Grade)/SUM(PossibleScore))*(Weight/100)) AS WeightedGrade
FROM studentItemGrades
WHERE DueDate>='2010-08-23'
AND DueDate<='2010-09-10'
AND CourseScheduleID=1
AND sDBID=519
AND Status>0
GROUP BY Weight
问题:我如何在WeighedGrade输出中对三个结果进行求和?顺便说一句,这是计算特定校园所有课程所有成绩的更大查询的一部分。
提前感谢您的帮助。
答案 0 :(得分:9)
您可以使用子查询,如下所示:
SELECT SUM(WeightedGrade) FROM
(
SELECT CourseScheduleID, sDBID, AssignedDate, DueDate, Weight,
((SUM(Grade)/SUM(PossibleScore))*(Weight/100)) AS WeightedGrade
FROM studentItemGrades
WHERE DueDate>='2010-08-23'
AND DueDate<='2010-09-10'
AND CourseScheduleID=1
AND sDBID=519
AND Status>0
GROUP BY Weight
) t1
答案 1 :(得分:1)
为了对三个结果求和,您需要使用另一个具有group by的select来重新查询此select的结果。这可以通过使用子查询使用单个sql语句来完成。
SELECT sq.CourseScheduleID, sq.sDBID, SUM(sq.WeightedGrade) as FinalGrade
FROM
(
SELECT CourseScheduleID, sDBID, AssignedDate, DueDate, Weight,
((SUM(Grade)/SUM (PossibleScore))*(Weight/100)) AS WeightedGrade
FROM studentItemGrades WHERE DueDate>='2010-08-23' AND DueDate<='2010-09-10'
AND CourseScheduleID=1 AND sDBID=519 AND Status>0 GROUP BY Weight
) AS sq
GROUP BY sq.CourseScheduleID, sq.sDBID