数据库练习

create database zuoye
use zuoye
create table student
(
sno varchar(20) not null,
sname varchar(20) not null,
ssex varchar(20) not null,
sbirthday datetime ,
class varchar(20) ,
)
insert into student values('108','曾华','男','1977-09-01','95033')
insert into student values('105','匡明','男','1975-10-02','95031')
insert into student values('107','王丽','女','1976-01-23','95033')
insert into student values('101','李军','男','1976-02-20','95033')
insert into student values('109','王芳','女','1975-02-10','95031')
insert into student values('103','陆君','男','1974-06-03','95031')
select *from student

create table course
(
cno varchar(20) not null,
cname varchar(20) not null,
tno varchar(20) not null,
)
insert into course values('3-105','计算机导论','825')
insert into course values('3-245','操作系统','804')
insert into course values('6-166','数字电路','856')
insert into course values('9-888','高等数学','831')
select *from course

create table score
(
sno varchar(20) not null,
cno varchar(20) not null,
degree decimal(4,1),
)
insert into score values('103','3-245',86)
insert into score values('105','3-245',75)
insert into score values('109','3-245',68)
insert into score values('103','3-105',92)
insert into score values('105','3-105',88)
insert into score values('109','3-105',76)
insert into score values('101','3-105',64)
insert into score values('107','3-105',91)
insert into score values('108','3-105',78)
insert into score values('101','6-166',85)
insert into score values('107','6-166',79)
insert into score values('108','6-166',81)
select *from score

create table teacher
(
tno varchar(20) not null,
tname varchar(20) not null,
tsex varchar(20) not null,
tbirthday datetime ,
prof varchar(20),
depart varchar(20) not null,
)
insert into teacher values('804','李诚','男','1958-12-02','副教授','计算机系')
insert into teacher values('856','张旭','男','1969-03-12','讲师','电子工程系')
insert into teacher values('825','王萍','女','1972-05-05','助教','计算机系')
insert into teacher values('831','刘冰','女','1977-08-14','助教','电子工程系')
select *from teacher

-- 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。
select*from student
--4、 查询Score表中成绩在60到80之间的所有记录。
select DEGREE from score where degree>60 and degree<80
--5、 查询Score表中成绩为85，86或88的记录。
select DEGREE from score where degree=85 or degree=88 or degree=86
select DEGREE from score where degree in (85,88,86)
--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。（子查询或者排序）
select* from score where degree in (select MAX(degree)from score)
select top 1*from score order by degree desc
--11、 查询每门课的平均成绩。
select cno,avg(degree) from Score group by cno
--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、查询分数大于70，小于90的Sno列。
select sno from score where degree>70 and degree<90
-- 14、查询所有学生的Sname、Cno和Degree列。
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 sno,cname,degree from score join course on score.sno =score.sno
--16、查询所有学生的Sname、Cname和Degree列。
select cname,sname,degree from score join student on student.sno=score.sno join course on score.cno=course.cno
-- 17.查询“95033”班学生的平均分。
select avg(degree) from score where Sno in (select sno from student where class='95033')