--1、 查询Student表中的所有记录的Sname、Ssex和Class列。
select sname,ssex,class from student
--2、 查询教师所有的单位即不重复的Depart列。
select distinct depart from teacher
--3、 查询Student表的所有记录。
--4、 查询Score表中成绩在60到80之间的所有记录。
select * from score where degree  between 60 and 80
--5、 查询Score表中成绩为85，86或88的记录。
select * from score where degree in(85,86,88)
--6、 查询Student表中“95031”班或性别为“女”的同学记录。
select * from student where class=‘95031‘ or ssex=‘女‘
--7、 以Class降序查询Student表的所有记录。
select * from student order by class desc
--8、 以Cno升序、Degree降序查询Score表的所有记录。
select * from score order by cno asc,degree desc
--9、 查询“95031”班的学生人数。
select COUNT(*) from student where class=‘95031‘
--10、查询Score表中的最高分的学生学号和课程号。
select * from score
select MAX(degree) from score   --92
select sno,cno from score where degree=(select MAX(degree) from score)
--11、查询‘3-105’号课程的平均分。
select AVG(degree) from score where cno=‘3-105‘
--12、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 cno,AVG(degree) from score where cno like ‘3%‘ group by cno having count(*)>=5

--13、查询最低分大于70，最高分小于90的Sno列。--假定按学生算。
select sno,MAX(degree),MIN(degree) from score group by sno having MAX(degree)<90 and MIN(degree)>70

--14、查询所有学生的Sname、Cno和Degree列。
select * from student
select * from score

select sname,cno,degree from student join score on student.sno = score.sno

--15、查询所有学生的Sno、Cname和Degree列。
select * from course
select * from score

select sno,cname,degree from course join score on course.cno = score.cno
--16、查询所有学生的Sname、Cname和Degree列。
select * from student
select * from course
select * from score

select sname,cname,degree from student
    join score on student.sno = score.sno
    join course on course.cno = score.cno

--17、查询“95033”班所选课程的平均分。
select * from student
select * from score
select sno from student where class=‘95033‘   --101,107,108
select * from score where sno in(101,107,108)
select AVG(degree) from score where sno in(select sno from student where class=‘95033‘ )

select AVG(score.degree) from student join score on student.sno = score.sno where student.class=‘95033‘

--18、假设使用如下命令建立了一个grade表：
create table grade(low  int,upp  int,rank  varchar(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 * from grade
select * from score
select sno,cno,rank from grade join score on score.degree>=grade.low and score.degree<=grade.upp
--19、查询选修“3-105”课程的成绩高于“109”号同学成绩的所有同学的记录。
select * from score
select * from score where cno=‘3-105‘  and degree>(select degree from score where cno=‘3-105‘ and sno=‘109‘)

select degree from score where cno=‘3-105‘ and sno=‘109‘   --76

--21、查询成绩高于学号为“109”、课程号为“3-105”的成绩的所有记录。
select *from score where degree >(select degree from score  where sno=‘109‘and cno=‘3-105‘)
--22、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‘) 
--23、查询“张旭“教师任课的学生成绩。
select *from score where cno=(select cno from course where tno=( select tno from teacher where tname=‘张旭‘))
--24、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=( select tno from course where cno in( select cno from score  group by cno having count(*)>5))
--25、查询95033班和95031班全体学生的记录。
select * from score where sno in( select sno from student where class in(‘95033‘,‘95031‘))
--26、查询存在有85分以上成绩的课程Cno.
select distinct cno from score where degree >85
--27、查询出“计算机系“教师所教课程的成绩表。
select *from score where cno in( select cno from course where tno in(select tno from teacher where depart =‘计算机系‘)
--28、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 
--29、查询选修编号为“3-105“课程且成绩至少高于选修编号为“3-245”的同学的Cno、Sno和Degree,并按Degree从高到低次序排序。
select cno from score group by cno having select degree from   where cno =‘3-105‘and degree >(select degree from score where cno=‘3-105‘ and sno=‘3-245‘)