sql练习

Student(S#,Sname,Sage,Ssex) 学生表

Course(C#,Cname,T#) 课程表

SC(S#,C#,score) 成绩表

Teacher(T#,Tname) 教师表

问题：
1、查询“001”课程比“002”课程成绩高的所有学生的学号；

select a.S# from (select s#,score from SC where C#=‘001’) a,(select s#,score

from SC where C#=‘002’) b

where a.score>b.score and a.s#=b.s#;

2、查询平均成绩大于60分的同学的学号和平均成绩；

select S#,avg(score)

from sc

group by S# having avg(score) >60;

3、查询所有同学的学号、姓名、选课数、总成绩；

select Student.S#,Student.Sname,count(SC.C#),sum(score)

from Student left Outer join SC on Student.S#=SC.S#

group by Student.S#,Sname

5、查询没学过“叶平”老师课的同学的学号、姓名；
distinct去重

select Student.S#,Student.Sname

from Student

where S# not in (select distinct( SC.S#) from SC,Course,Teacher where SC.C#=Course.C# and Teacher.T#=Course.T# and Teacher.Tname=‘叶平’);

8、查询课程编号“002”的成绩比课程编号“001”课程低的所有同学的学号、姓名；

select tblstudent.StuId,tblstudent.StuName from tblstudent where
(
(select tblscore.Score from tblscore where tblstudent.StuId=tblscore.StuId and tblscore.CourseId=‘002’)
<(select tblscore.Score from tblscore where tblstudent.StuId=tblscore.StuId and tblscore.CourseId=‘001’)
)

11、查询至少有一门课与学号为“1001”的同学所学相同的同学的学号和姓名；

select S#,Sname from Student,SC where Student.S#=SC.S# and C# in （select C# from SC where S#=‘1001’）;

14、查询和“1002”号的同学学习的课程完全相同的其他同学学号和姓名；

select s#,sname from student
where s# in
(select S# from SC where C# in (select C# from SC where S#=‘1002’)group by S# having count(*)=(select count(**) from SC where S#=‘1002’)