mysql数据库表的查询

一、            设有一数据库，包括四个表：学生表（Student）、课程表（Course）、成绩表（Score）以及教师信息表（Teacher）。四个表的结构分别如表1-1的表（一）~表（四）所示，数据如表1-2的表（一）~表（四）所示。用SQL语句创建四个表并完成相关题目。

表1-1数据库的表结构 

表（一）Student (学生use)

属性名	数据类型	可否为空	含 义
Sno	varchar (20)	否	学号（主码）
Sname	varchar (20)	否	学生姓名
Ssex	varchar (20)	否	学生性别
Sbirthday	Datetime	可	学生出生年月
Class	varchar (20)	可	学生所在班级

表（二）Course（课程表）

属性名	数据类型	可否为空	含 义
Cno	varchar (20)	否	课程号（主码）
Cname	varchar (20)	否	课程名称
Tno	varchar (20)	否	教工编号

表（三）Score(成绩表)

属性名	数据类型	可否为空	含 义
Id	Int		主键 自增
Sno	varchar (20)	否	学号
Cno	varchar (20)	否	课程号
Degree	Decimal(4,1)	可	成绩
//主码：Sno+ Cno

表（四）Teacher(教师表)

属性名	数据类型	可否为空	含 义
Tno	varchar (20)	否	教工编号（主码）
Tname	varchar (20)	否	教工姓名
Tsex	varchar (20)	否	教工性别
Tbirthday	datetime	可	教工出生年月
Prof	varchar (20)	可	职称
Depart	varchar (20)	否	教工所在部门

表1-2数据库中的数据

表（一）Student

Sno	Sname	Ssex	Sbirthday	class
108	曾华	男	1977-09-01	95033
105	匡明	男	1975-10-02	95031
107	王丽	女	1976-01-23	95033
101	李军	男	1976-02-20	95033
109	王芳	女	1975-02-10	95031
103	陆君	男	1974-06-03	95031

表（二）Course

Cno	Cname	Tno
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

表（三）Score

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 * from score where degree > 68 and cno = ‘3-105’ order by degree desc;

Select min(degree) from score where cno = ‘3-245’;

Sno	Cno	Degree
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

表（四）Teacher

Tno	Tname	Tsex	Tbirthday	Prof	Depart
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

包含步骤思路

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 60<degree and degree<80;

select degree 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 degree from score where degree=85 or degree=86 or degree=88;

select degree 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。升序（asc可省略）

select * from score order by cno,degree desc;

9、查询“95031”班的学生人数。

select count(sname) 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）

子查询

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,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),cno from score where cno like "3%" group by cno having count(cno)>=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.cno=course.cno;

16、查询所有学生的Sname、Cname和Degree列。

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

17、查询“95033”班学生的平均分。

select avg(degree) from Score where Sno in (select sno from student where class='95033');

select avg(degree) from score join student on student.sno=score.sno where class='95033';

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 cno from score where cno="3-105";

select degree from score where sno="109"and cno="3-105";

select * from score where cno in (select cno from score where cno="3-105") and degree>(select degree from score where sno="109"and cno="3-105");

select * from student join score on student.sno=score.sno where score.cno="3-105" and score.degree>(select degree from score where sno="109"and cno="3-105");

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 sno from score group by sno having count(cno)>1;

select max(degree) from score;

select * from score where degree<(select max(degree) from score) and sno in (select sno from score group by sno having count(cno)>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 student join score on student.sno=score.sno 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 year(sbirthday)=(select year(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 in (select tno from teacher where tname="张旭");

select degree from score where cno in (select cno from course where tno in (select tno from teacher where tname="张旭"));

select sname,degree from student join score on student.sno=score.sno join course on course.cno=score.cno join teacher on teacher.tno=course.tno where teacher.tname="张旭";

23、查询考计算机导论的学生成绩

select cno from course where cname like "计算机导论";

select sno,degree from score where cno in (select cno from course where cname like "计算机导论");

24、查询 所有的列/字段 从 成绩表(score) 条件是

select * from score;

25、课程名(cname)称为计算机导论 的课程编号

select cno from course where cname="计算机导论";

26、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 in (select tno from teacher where tname="李诚");

27、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");

28、查询选修某课程的同学人数多于5人的教师姓名。

select cno from score group by cno having count(sno)>5;

select tno from course where cno=(select cno from score group by cno having count(sno)>5);

select tname from teacher where tno=(select tno from course where cno=(select cno from score group by cno having count(sno)>5));

29、查询95033班和95031班全体学生的记录。

select sno from student where class="95033" or class="95031";

select * from student join score on student.sno=score.sno where  student.sno in (select sno from student where class="95033" or class="95031");

30、查询成绩表中存在有85分以上成绩的课程Cno.

select distinct cno from score where degree>85;

31、查询出“计算机系“教师所教课程的成绩表。

select tno 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 cno,degree from score where cno in (select cno from course where tno in (select tno from teacher where depart="计算机系"));

32、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 cno,sno,degree from score where cno="3-105" and degree>(select max(degree) from score where cno="3-245");

33、查询所有教师和同学的name、sex和birthday.

select sname,ssex,sbirthday from student union select tname,tsex,tbirthday from teacher;

34、查询所有“女”教师和“女”同学的name、sex和birthday.

select sname,ssex,sbirthday from student where ssex="女" union select tname,tsex,tbirthday from teacher where tsex="女";

35、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 * from score where degree<(select avg(degree) from score where cno="3-105");

36、查询所有任课教师的Tname和Depart.

select distinct cno from score;

select tno from course where cno in (select distinct cno from score);

select tname,depart from teacher where tno in (select tno from course where cno in (select distinct cno from score));

37、查询所有未讲课的教师的Tname和Depart.

select tname,depart from teacher where tno in (select tno from course where cno not in (select distinct cno from score));

38、查询至少有2名男生的班号。

select class from student group by class having count(ssex)>=2;

39、查询Student表中不姓“王”的同学记录。

select * from student where sname not like "王%";

40、查询Student表中每个学生的姓名和年龄。

select sname,year(now()) - year(sbirthday) as 年龄 from student;

41、查询Student表中最大和最小的Sbirthday日期值。

select min(sbirthday) as 最大,max(sbirthday) as 最小 from student;

42、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;

43、查询“男”教师及其所上的课程。

select * from teacher where tsex="男";

select tno from teacher where tsex="男";

select cname from course where tno in (select tno from teacher where tsex="男");

select tname,cname from teacher join course on teacher.tno=course.tno where tsex="男";

44、查询最高分同学的Sno、Cno和Degree列。

select max(degree) from score;

select sno,cno,degree from score where degree=(select max(degree) from score);

45、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 in (select ssex from student where sname="李军");

46、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 in (select ssex from student where sname="李军") and class in (select class from student where sname="李军");

47、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 student where ssex="男";

select * from score where cno in (select cno from course where cname="计算机导论") and sno in(select sno from student where ssex="男");