有学生头选课系统,数据库中有四个表,分别为: Student(S#, Sname, Sage, Ssex)

Question

1. 有学生头选课系统，数据库中有四个表，分别为：Student(S#, Sname, Sage, Ssex)学生表Course(C#,C#name,T#)课程表SC(S#, C#,Score)成绩表;Teacher(T#, Tname)教师表问题：（1） 查询平均成绩大于60份的同学的序号和平均成绩；
（2） 查询两门以上不及格课程的同学的学号及其平均成绩；
（3） 查询没学过“叶平”老师课的同学的学号、姓名；

Answer 1

1
select a.S#, avg(b.Score) Student a,SC b where a.S#=b.S# group by a.S#
having avg(b.Score) > 60

2
select a.S#, avg(b.Score) Student a,SC b where a.S#=b.S# and S# IN
(
select S# from SC where Score <60 group by S# having count(*) > 2
)
group by a.S#

3
select S#,Sname from where S# not in
(select a.S# from Student a,Course b,SC c,Teacher d
where
a.S#=c.S# and
b.C#=c.C# and
b.T#=d.T# and
d.Tname='叶平')本回答被网友采纳

Answer 2

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