50个SQL语句(MySQL版)问题二十二
--------------------------表结构--------------------------
student(StuId,StuName,StuAge,StuSex) 学生表
teacher(TId,Tname) 教师表
course(CId,Cname,C_TId) 课程表
sc(SId,S_CId,Score) 成绩表
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问题二十二:查询如下课程成绩第3名到第6名的学生成绩单:企业管理(001),马克思(002),UML(003),数据库(004)格式:[学生ID],[学生姓名],企业管理,马克思,UML,数据库,平均成绩
SELECT stu.StuId,stu.StuName,BM.Score
AS BM,Marx.Score AS Marx,UML.Score AS UML,DB.Score AS DB,(IFNULL(BM.Score,
0)+IFNULL(Marx.Score,0)+IFNULL(UML.Score,0)+IFNULL(DB.Score,0))/(
SUM(CASEWHEN IFNULL(BM.Score,0)=0THEN0ELSE1END)+SUM(CASEWHEN IFNULL(Marx.Score,0)=0THEN0ELSE1END)+
SUM(CASEWHEN IFNULL(UML.Score,0)=0THEN0ELSE1END)+
SUM(CASEWHEN IFNULL(DB.Score,0)=0THEN0ELSE1END)) AS AvgScore
FROM student stu
LEFTJOIN sc AS BM ON BM.SId=stu.StuId AND BM.S_CId="001"
LEFTJOIN sc AS Marx ON Marx.SId=stu.StuId AND Marx.S_CId="002"
LEFTJOIN sc AS UML ON UML.SId=stu.StuId AND UML.S_CId="003"
LEFTJOIN sc AS DB ON DB.SId=stu.StuId AND DB.S_CId="004"
GROUPBY stu.StuId
ORDERBY AvgScore DESC
LIMIT 2,4;
答案仅供参考,不一定完全正确,若发现错误或有更好的,欢迎评论,互相交流,一起成长!!!
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