SQL面试题

Student(S#,Sname,Sage,Ssex) 学生表     S#：学号；Sname：学生姓名；Sage：学生年龄；Ssex：学生性别
Course(C#,Cname,T#) 课程表                C#：课程编号；Cname：课程名字；T#：教师编号
SC(S#,C#,score) 成绩表                        S#：学号；C#,课程编号；score：成绩
Teacher(T#,Tname) 教师表                    T#：教师编号； Tname：教师名字

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 

4、查询姓“李”的老师的个数； 
select count(distinct(Tname)) 
from Teacher 
where Tname like '李%'; 

5、查询没学过“叶平”老师课的同学的学号、姓名； 
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'); 

6、查询学过“001”并且也学过编号“002”课程的同学的学号、姓名； 
select Student.S#,Student.Sname from Student,SC 
where Student.S#=SC.S# and SC.C#='001'and exists( Select * from SC as SC_2 where SC_2.S#=SC.S# and SC_2.C#='002'); 

7、查询学过“叶平”老师所教的所有课的同学的学号、姓名； 
a、查询“叶平”老师所教的所有课
select C# from Course,Teacher where Teacher.T#=Course.T# and Tname='叶平' =》AAA
b、select Student.S#,Student.name from Student left Outer join SC on Student.S#=SC.S# and SC.C# in (AAA)