数据库练习题重点整理

查询Score表中至少有5名学生选修的并以3开头的课程的平均分数：
select avg(degree) from score where cno like‘3%‘ and cno in(select cno from score group by cno having count(*)>4)

select avg(degree) from score group by cno having count(*)>4 and cno like ‘3%‘

假设使用如下命令建立了一个grade表：
create table grade(low  int(3),upp  int(3),rank  char(1))
insert into grade values(90,100,’A’)
insert into grade values(80,89,’B’)
insert into grade values(70,79,’C’)
insert into grade values(60,69,’D’)
insert into grade values(0,59,’E’)
现查询所有同学的Sno、Cno和rank列。
select sno,cno,rank from score,grade where degree between low and upp

查询score中选学多门课程的同学中分数为非最高分成绩的记录。
select * from score where sno in(select sno from score group by sno having count(*)>1) and degree<(select max(degree) from score)

select * from score a where sno in(select sno from score group by sno having count(*)>1) and degree<(select max(degree) from score b where b.cno = a.cno)

查询和学号为108的同学同年出生的所有学生的Sno、Sname和Sbirthday列。
select sno,sname,sbirthday from student where YEAR(sbirthday) = (select YEAR(sbirthday) from student where sno=‘108‘)

查询选修某课程的同学人数多于5人的教师姓名。
select tname from teacher where tno in(select tno from course where cno in(select cno from score group by cno having count(*)>5))

查询“计算机系”与“电子工程系“不同职称的教师的Tname和Prof。
select Tname,Prof from Teacher a where Prof not in(select Prof from Teacher b where a.Depart!=b.Depart)