#建学生信息表student create table student ( sno varchar(20) not null primary key, sname varchar(20) not null, ssex varchar(20) not null, sbirthday datetime, class varchar(20) ); #建立教师表 create table teacher ( tno varchar(20) not null primary key, tname varchar(20) not null, tsex varchar(20) not null, tbirthday datetime, prof varchar(20), depart varchar(20) not null ); #建立课程表course create table course ( cno varchar(20) not null primary key, cname varchar(20) not null, tno varchar(20) not null, foreign key(tno) references teacher(tno) ); #建立成绩表 create table score (
id int auto_increment primary key, sno varchar(20) not null, foreign key(sno) references student(sno), cno varchar(20) not null, foreign key(cno) references course(cno), degree decimal ); #添加学生信息 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'); #添加教师表 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'); #添加课程表 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'); #添加成绩表 insert into score values(1,'103','3-245','86'); insert into score values(2,'105','3-245','75'); insert into score values(3,'109','3-245','68'); insert into score values(4,'103','3-105','92'); insert into score values(5,'105','3-105','88'); insert into score values(6,'109','3-105','76'); insert into score values(7,'103','3-105','64'); insert into score values(8,'105','3-105','91'); insert into score values(9,'109','3-105','78'); insert into score values(10,'103','6-166','85'); insert into score values(11,'105','6-166','79'); insert into score values(12,'109','6-166','81');
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；#distinct意思是过滤不重复的
4、 查询Score表中成绩在60到80之间的所有的学生记录。
select student.sname from score left join student on student.sno=score.sno where degree>60 and degree<81 group by student.sname
5、 查询Score表中成绩为85，86或88的学生记录
select student.sname from score left join student on student.sno=score.sno where Degree in(85,86,88) group by student.sname
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; #desc 是降序所默认为升序
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 #asc为升序，默认为asc desc为降序
14、 查询所有学生的Sname、Cno和Degree列。
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 cno,sno from score where degree=(select max(degree) from score);
select cno,sno from score order by degree desc limit 0,1; #limit 0,1 意思是区一行 0,2就是取二行
11、 查询每门课的平均成绩
select 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 avg(degree) from score where cno like '3%' and cno in(select cno from score group by cno having count(*)>=5);
#like 模糊查询里面包含3的
13 查询分数大于70，小于90的Sno列。
select sno from score where degree>70 and degree<90 group by sno;
14、 查询所有学生的Sname、Cno和Degree列。
15、 查询所有学生的Sno、Cname和Degree列。