哪位高手能给点SQL高级查询的练习题，不胜感谢

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 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；   select S#,Sname   from Student   where S# in (select S# from SC ,Course ,Teacher where SC.C#=Course.C# and Teacher.T#=Course.T# and Teacher.Tname='叶平' group by S# having count(SC.C#)=(select count(C#) from Course,Teacher  where Teacher.T#=Course.T# and 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 S#,Sname from (select Student.S#,Student.Sname,score ,(select score from SC SC_2 where SC_2.S#=Student.S# and SC_2.C#='002') score2   from Student,SC where Student.S#=SC.S# and C#='001') S_2 where score2 <score; 9、查询所有课程成绩小于60分的同学的学号、姓名；   select S#,Sname   from Student   where S# not in (select Student.S# from Student,SC where S.S#=SC.S# and score>60); 10、查询没有学全所有课的同学的学号、姓名；     select Student.S#,Student.Sname     from Student,SC     where Student.S#=SC.S# group by  Student.S#,Student.Sname having count(C#) <(select count(C#) from Course); 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'; 12、查询至少学过学号为“001”同学所有一门课的其他同学学号和姓名；     select distinct SC.S#,Sname     from Student,SC     where Student.S#=SC.S# and C# in (select C# from SC where S#='001'); 13、把“SC”表中“叶平”老师教的课的成绩都更改为此课程的平均成绩；     update SC set score=(select avg(SC_2.score)     from SC SC_2     where SC_2.C#=SC.C# ) from Course,Teacher where Course.C#=SC.C# and Course.T#=Teacher.T# and Teacher.Tname='叶平'); 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# from SC where C# in (select C# from SC where S#='1002')     group by S# having count(*)=(select count(*) from SC where S#='1002'); 15、删除学习“叶平”老师课的SC表记录；     Delect SC     from course ,Teacher      where Course.C#=SC.C# and Course.T#= Teacher.T# and Tname='叶平'; 16、向SC表中插入一些记录，这些记录要求符合以下条件：没有上过编号“003”课程的同学学号、2、     号课的平均成绩；     Insert SC select S#,'002',(Select avg(score)     from SC where C#='002') from Student where S# not in (Select S# from SC where C#='002'); 17、按平均成绩从高到低显示所有学生的“数据库”、“企业管理”、“英语”三门的课程成绩，按如下形式显示： 学生ID,,数据库,企业管理,英语,有效课程数,有效平均分     SELECT S# as 学生ID         ,(SELECT score FROM SC WHERE SC.S#=t.S# AND C#='004') AS 数据库         ,(SELECT score FROM SC WHERE SC.S#=t.S# AND C#='001') AS 企业管理         ,(SELECT score FROM SC WHERE SC.S#=t.S# AND C#='006') AS 英语         ,COUNT(*) AS 有效课程数, AVG(t.score) AS 平均成绩     FROM SC AS t     GROUP BY S#     ORDER BY avg(t.score)  18、查询各科成绩最高和最低的分：以如下形式显示：课程ID，最高分，最低分     SELECT L.C# As 课程ID,L.score AS 最高分,R.score AS 最低分     FROM SC L ,SC AS R     WHERE L.C# = R.C# and         L.score = (SELECT MAX(IL.score)                       FROM SC AS IL,Student AS IM                       WHERE L.C# = IL.C# and IM.S#=IL.S#                       GROUP BY IL.C#)         AND         R.Score = (SELECT MIN(IR.score)                       FROM SC AS IR                       WHERE R.C# = IR.C#                   GROUP BY IR.C#                     ); 19、按各科平均成绩从低到高和及格率的百分数从高到低顺序     SELECT t.C# AS 课程号,max(course.Cname)AS 课程名,isnull(AVG(score),0) AS 平均成绩         ,100 * SUM(CASE WHEN  isnull(score,0)>=60 THEN 1 ELSE 0 END)/COUNT(*) AS 及格百分数     FROM SC T,Course     where t.C#=course.C#     GROUP BY t.C#     ORDER BY 100 * SUM(CASE WHEN  isnull(score,0)>=60 THEN 1 ELSE 0 END)/COUNT(*) DESC 20、查询如下课程平均成绩和及格率的百分数(用"1行"显示): 企业管理（001），马克思（002），OO&UML （003），数据库（004）     SELECT SUM(CASE WHEN C# ='001' THEN score ELSE 0 END)/SUM(CASE C# WHEN '001' THEN 1 ELSE 0 END) AS 企业管理平均分         ,100 * SUM(CASE WHEN C# = '001' AND score >= 60 THEN 1 ELSE 0 END)/SUM(CASE WHEN C# = '001' THEN 1 ELSE 0 END) AS 企业管理及格百分数         ,SUM(CASE WHEN C# = '002' THEN score ELSE 0 END)/SUM(CASE C# WHEN '002' THEN 1 ELSE 0 END) AS 马克思平均分         ,100 * SUM(CASE WHEN C# = '002' AND score >= 60 THEN 1 ELSE 0 END)/SUM(CASE WHEN C# = '002' THEN 1 ELSE 0 END) AS 马克思及格百分数         ,SUM(CASE WHEN C# = '003' THEN score ELSE 0 END)/SUM(CASE C# WHEN '003' THEN 1 ELSE 0 END) AS UML平均分         ,100 * SUM(CASE WHEN C# = '003' AND score >= 60 THEN 1 ELSE 0 END)/SUM(CASE WHEN C# = '003' THEN 1 ELSE 0 END) AS UML及格百分数         ,SUM(CASE WHEN C# = '004' THEN score ELSE 0 END)/SUM(CASE C# WHEN '004' THEN 1 ELSE 0 END) AS 数据库平均分         ,100 * SUM(CASE WHEN C# = '004' AND score >= 60 THEN 1 ELSE 0 END)/SUM(CASE WHEN C# = '004' THEN 1 ELSE 0 END) AS 数据库及格百分数   FROM SC