2、查询从来没有参加任何考试的学生的信息。
select * from student where number not in (select number from chengji)
3、查询有考试成绩纪录的学生的信息.
select * from student where number    in (select number from chengji)
4、将所有大连地区学生的课程编号为3的课程成绩加10分。
update chengji set score=score+10 where scorenumber=3
5、删除所有C#课的成绩。
delete chengji where scorenumber=(select scorenumber from score where kemu='C#')
6、查询课程编号为3的课程的平均成绩，显示有此门课程成绩的学生编号，成绩及距平均分之间的差值。
select number,score-(select avg(score) from chengji where scorenumber=3) from chengji where scorenumber=3
7、查询参加了所有考试的学生的姓名。
select name from student where number in( select max(number) from chengji group by number)
8、查询有成绩纪录的学生人数。
    selectnumber ,name from student where number in
( select max(number) from chengji     group by number having count(scorenumber)=(select count(*) from score) )
9、查询有2门以上成绩的学生的姓名和联系方式。
select name,lianxidianhua from student where number in( select number from chengji group by number having count(scorenumber)>2)
10、查询哪些学生有c#考试成绩，显示这些学生的姓名。
select name from student where number in( select number from chengji where scorenumber =(select scorenumber from score where kemu='c#'))
给结果集添加编号
11.查询出科目中教师的编号，同时增加序号。
        select 序号=(select count(*) from score as a where a.scorenumber<=b.scorenumber ),teacherid    from score as b
        select 序号=identity(1,1),teachername into #newtable from score
12.随机显示学生信息表中的两条数据：使用newid（）函数
select top 2 * from student    order by newid()
13.查询出联系电话为null的学生信息，联系电话用‘无’代替。
select name,isnull(convert(char(20),lianxidianhua),'无') from student    
14.将查询出的地区为大连的都显示为null
select name,nullif(diqu,'大连') from student
15.查询科目平均成绩超过70分的教师姓名。
select teachername from teacherinfo where teacherid in    
(select teacherid from score where scorenumber in
(select scorenumber from chengji group by scorenumber having avg(score)>=70))