#建表内容如下：
表（一）student（学生)
create table student(
sno varchar(20) primary key not null comment'学号(主码)',
sname varchar(20) not null comment'学生姓名',
ssex varchar(20) not null comment'学生性别',
sbirthday datetime comment'学生出生年月',
class varchar(20) comment'学生所在班级'
);
表（二）Course（课程表）
create table course(
cno varchar(20) primary key not null comment'课程号(主码)',
cname varchar(20) not null comment'课程名称',
tno varchar(20) not null comment'教工编号'
);
表（三）Score(成绩表)
create table score(
id int primary key auto_increment comment'主键自增',
sno varchar(20) not null comment'学号',
cno varchar(20) not null comment'课程号',
degree Decimal(4,1) comment'成绩'
);
表（四） teacher(教师表)
create table teacher(
tno varchar(20) primary key not null comment'教工编号(主码)',
tname varchar(20) not null comment'教工姓名',
tsex varchar(20) not null comment'教工性别',
tbirthday datetime comment'教工出生年月',
prof varchar(20) comment'职称',
depart varchar(20) not null comment'教工所在部门'
);
#插入内容如下：
学生表数据的插入：
insert into student values
('108','曾华','男','1977-09-01','95033'),
('105','匡明','男','1977-09-01','95031'),
('107','王丽','女','1977-09-01','95033'),
('101','李军','男','1977-09-01','95033'),
('109','王芳','女','1977-09-01','95031'),
('103','陆君','男','1977-09-01','95031');
课程表数据的插入：
insert into course values
('3-105','计算机导论','825'),
('3-245','操作系统','804'),
('6-166','数字电路','856'),
('9-888','高等数学','831');
成绩表数据的插入：
select cno from score group by cno;
insert into score(sno,cno,degree) values
('103','3-245','86'),
('105','3-245','75'),
('109','3-245','68'),
('103','3-105','92'),
('105','3-105','88'),
('109','3-105','76'),
('101','3-105','64'),
('107','3-105','91'),
('108','3-105','78'),
('101','6-166','85'),
('107','6-166','79'),
('108','6-166','81');
教师表数据的插入：
insert into teacher values
('804','李诚','男','1958-12-02','副教授','计算机系'),
('856','张旭','男','1969-03-12','讲师','电子工程系'),
('825','王萍','女','1972-05-05','助教','计算机系'),
('831','刘冰','女','1977-08-14','助教','电子工程系');
练习题及答案：
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 * 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 * 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 like '95031' or ssex like '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 class,count(*) from student where class='95031' group by class;
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 order by degree desc limit 1;
select max(degree) from score
select * from score where degree = (select max(degree) from score);
select sno,cno from score where degree = (select max(degree) from score);
11、 查询每门课的平均成绩。
select cno,count(*),avg(degree) from score group by cno;
多条查询
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。
方法一：select n.cno,n.num,n.avg from (select count(*) num,cno,avg(degree) avg from score group by cno) n where n.num >=5;
方法二：select cno,count(*),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,degree from score where degree>70 and degree<90;
select group_concat(sno) from score where degree>70 and degree<90;
14、查询所有学生的Sname、Cno和Degree列。(多表查询)
student.sname,course.cno,score.degree
select student.sname,course.cno,score.degree from student,course,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 sno,cname,degree from score join course on course.cno = score.cno;
select student.sname,score.cno,score.degree from score left join student on score.sno=student.sno;
16、查询所有学生的Sname、Cname和Degree列。
student.sname,course.cname,score.degree;
方法一：select student.sname,cname,degree from student join score on student.sno = score.sno join course on course.cno = score.cno;
方法二：select sname,cname,degree from course join (select cno,sname,degree from student join score on student.sno = score.sno) new_table on course.cno = new_table.cno;
17、查询“95033”班学生的平均分。
方法一： select avg(degree) from score where sno in(select sno from student where class = '95033');
方法二：select avg(degree),class from student join score on student.sno = score.sno where class like '95033' group by class;
18、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 sno,cno,degree from score where cno like '3-105' and degree > (select degree from score where cno like '3-105' and sno like '109');
19、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 a where Sno in (select Sno from score group by Sno having count(*)>1 ) and Degree not in (select max(Degree) from score a where Sno in (select Sno from score group by Sno having count(*)>1 ));
20、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 degree from score where sno = '109' and cno = '3-105';
select * from score where degree > (select degree from score where sno = '109' and cno = '3-105');
21、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 sbirthday from student where sno = '108';
select sno,sname,sbirthday from student where sbirthday = (select sbirthday from student where sno = '108');
22、查询“张旭“教师任课的学生成绩（姓名）。
select tno from teacher where tname = '张旭';
select cno from course where tno = (select tno from teacher where tname = '张旭');
select sno,degree from score where cno = (select cno from course where tno = (select tno from teacher where tname = '张旭'));
select student.sno,degree,sname from score join student on score.sno = student.sno where student.sno in (select sno from score where cno = (select cno from course where tno = (select tno from teacher where tname = '张旭')));
23、查询考计算机导论的学生成绩
select cno from course where cname = '计算机导论';
select sno,degree from score where cno = (select cno from course where cname = '计算机导论');
24、查询李诚老师教的课程名称
select tno from teacher where tname = '李诚';
select cname from course where tno = (select tno from teacher where tname = '李诚');
25、教高等数学的老师是哪个系的
select tno from course where cname = '高等数学';
select depart from teacher where tno = (select tno from course where cname = '高等数学');
26、查询选修某课程的同学人数多于5人的教师姓名。
select cno,count(*) from score group by cno having count(*)>=5;
select tno from course where cno = (select cno from score group by cno having count(*)>=5);
select tname from teacher where tno = (select tno from course where cno = (select cno from score group by cno having count(*)>=5));
27、查询95033班和95031班全体学生的记录。
select * from student group by class having count(*);
select * from student order by class desc;
28、查询成绩表中存在有85分以上成绩的课程Cno.
select cno,degree from score where degree>85;
29、查询出“计算机系“教师所教课程的成绩表。
select tno,tname from teacher where depart = '计算机系'
select cno from course where tno in (select tno from teacher where depart = '计算机系');
select sno,cno,degree from score where cno in (select cno from course where tno in (select tno from teacher where depart = '计算机系'));
30、查询选修编号为“3-105”且成绩高于选修编号为“3-245”课程的同学的 Cno、Sno和Degree.
select max(degree) from score where cno = '3-245';
select cno,sno,degree from score where cno = '3-105' and degree > (select max(degree) from score where cno = '3-245');
31、查询所有教师和同学的name、sex和birthday.
select tname as name,tsex as sex,tbirthday as birthday from teacher union select sname,ssex,sbirthday from student;
32、查询所有“女”教师和“女”同学的name、sex和birthday.
select tname as name,tsex as sex,tbirthday as birthday from teacher where tsex = '女'
union
select sname,ssex,sbirthday from student where ssex = '女';
33、查询所有成绩比3-105课程平均成绩低的同学的成绩表。
select avg(degree) from score where cno = '3-105';
select degree from score where degree < (select avg(degree) from score where cno = '3-105');
34、查询所有任课教师的Tname和Depart.
select tname,depart from teacher;
35、查询所有未讲课的教师的Tname和Depart.
select tno from course group by tno;
select tname,depart from teacher where not exists(select tno from course group by tno);
36、查询至少有2名男生的班号。
select ssex,class from student where ssex = '男' group by class;
select class from student where exists ((select ssex,class from student where ssex = '男' group by class) * 2);
37、查询Student表中不姓“王”的同学记录。
select sname from student where sname like '王%'
select sname from student where sname not in (select sname from student where sname like '王%');
38、查询Student表中每个学生的姓名和年龄。
select sname,floor(datediff(curdate(),sbirthday)/365.2422) from student;
39、查询Student表中最大和最小的Sbirthday日期值。
select max(sbirthday) as '最大日期' , min(sbirthday) as '最小日期' from student;
update student set sbirthday = '1995-07-11' where sno = '108';
update student set sbirthday = '1820-05-01' where sno = '105';
40、以班号和年龄从大到小的顺序查询Student表中的全部记录。
select * from student order by class desc,sbirthday desc;
41、查询“男”教师及其所上的课程。
select tno from teacher where tsex = '男';
select cname from course where tno in (select tno from teacher where tsex = '男');
42、查询最高分同学的Sno、Cno和Degree列。
select max(degree) from score
select score.sno,cno,degree from student
join
score
on student.sno = score.sno
where degree = (select max(degree) from score);
43、查询和“李军”同性别的所有同学的Sname.
select ssex from student where sname = '李军';
select sname from student where ssex = (select ssex from student where sname = '李军');
44、查询和“李军”同性别并同班的同学Sname.
select class from student where sname = '李军';
select sname from student where ssex = (select ssex from student where sname = '李军') and class = (select class from student where sname = '李军');
45、查询所有选修“计算机导论”课程的“男”同学的成绩表。
select cno from course where cname = '计算机导论';
select sno from score where cno = (select cno from course where cname = '计算机导论');
select sname from student where sno in (select sno from score where cno = (select cno from course where cname = '计算机导论')) and ssex = '男';
（以上的答案可能会有纰漏，仅供大家参考）
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