代码查询一般思路：
根据什么条件查询什么
用到哪几个表，
第一步，查什么，
第二步，查什么……
组合
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 (学生表)
|
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（外码） |
表（三）Score(成绩表)
|
属性名 |
数据类型 |
可否为空 |
含 义 |
|
Sno |
varchar (20) |
否 |
学号（外码） |
|
Cno |
varchar (20) |
否 |
课程号（外码） |
|
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
|
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 |
1、 查询Student表中的所有记录的Sname、Ssex和Class列。
2、 查询教师所有的单位即不重复的Depart列。
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。
5、 查询Score表中成绩为85，86或88的记录。
6、 查询Student表中“95031”班或性别为“女”的同学记录。
7、 以Class降序查询Student表的所有记录。
8、 以Cno升序、Degree降序查询Score表的所有记录。
9、 查询“95031”班的学生人数。
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）
11、 查询每门课的平均成绩。
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。
13、查询分数大于70，小于90的Sno列。
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。
16、查询所有学生的Sname、Cname和Degree列。
17、 查询“95033”班学生的平均分。
18、 假设使用如下命令建立了一个grade表：
create table grade(low int(3),upp int(3),rank char(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。
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。
20、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。
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。
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。
23、查询“张旭“教师任课的学生成绩。
24、查询选修某课程的同学人数多于5人的教师姓名。
25、查询95033班和95031班全体学生的记录。
26、 查询存在有85分以上成绩的课程Cno.
27、查询出“计算机系“教师所教课程的成绩表。
28、查询“计算机系”与“电子工程系“不同职称的教师的Tname和Prof。
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。
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.
31、 查询所有教师和同学的name、sex和birthday.
32、查询所有“女”教师和“女”同学的name、sex和birthday.
33、 查询成绩比该课程平均成绩低的同学的成绩表。
34、 查询所有任课教师的Tname和Depart.
35 、 查询所有未讲课的教师的Tname和Depart.
36、查询至少有2名男生的班号。
37、查询Student表中不姓“王”的同学记录。
38、查询Student表中每个学生的姓名和年龄。
39、查询Student表中最大和最小的Sbirthday日期值。
40、以班号和年龄从大到小的顺序查询Student表中的全部记录。
41、查询“男”教师及其所上的课程。
42、查询最高分同学的Sno、Cno和Degree列。
43、查询和“李军”同性别的所有同学的Sname.
44、查询和“李军”同性别并同班的同学Sname.
45、查询所有选修“计算机导论”课程的“男”同学的成绩表。
先用代码建表：
(建表也可以用设计界面，但既然作为一个程序员,写代码还是比较有趣的)
主表建在从表前；
#学生表 create table student( sno varchar(20) primary key, sname varchar(20) not null, ssex varchar(20) not null, sbirthday datetime, calss varchar(20) ); #教师表 create table teacher( tno varchar(20) primary key, tname varchar(20) not null, tsex varchar(20) not null, tbirthday datetime, prof varchar(20), dapart varchar(20) not null ); #课程表 create table course( cno varchar(20) primary key, cname varchar(20) not null, tno varchar(20) not null, foreign key(tno) references teacher(tno) ); #成绩表 create table score( ids 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), dagree decimal(4,1) ); 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','路君','男','1974-06-03','95031'); insert into teacher values('804','李成','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'); 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'); 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'); #grade表 create table grade( low int(3), upp int(3), rank char(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');
答案：
1.select Sname,Ssex,Class from Student 2.select distinct depart from Teacher 3.select * from Student 4.select * from Score where Degree>=60 and Degree<=80 select * from Score where Degree between 60 and 80 5.select * from Score where Degree in(85,86,88) 6.select * from Student where Class = '95031' or Ssex = '女' 7.select * from Student order by Class desc 8.select * from Score order by Cno,Degree desc 9.select count(*) from Student where Class='95031' 10.select Sno,Cno from Score where Degree=(select max(Degree) from Score) 11.select Cno,avg(Degree) from Score group by Cno 12.select avg(Degree) from Score where Cno in (select Cno from Score group by Cno having count(*)>5) and Cno like '3%' group by Cno select avg(Degree) from Score where Cno like '3%' group by Cno having count(*)>5 13.select Sno from Score where Degree between 70 and 90 14.select Sname,Cno,Degree from Score join Student on Student.Sno = Score.Sno 15.select Sno,Cname,Degree from Score join Course on Score.Cno = Course.Cno 16.select Sname,Cname,Degree from Score join Student on Student.Sno = Score.Sno join Course on Score.Cno = Course.Cno 17.select avg(Degree) from Score where Sno in (select Sno from Student where Class = '95033') 18.select Sno,Cno,rank from Score join grade on Score.Degree between low and upp 19.select * from Score where Cno ='3-105' and Degree>(select Degree from Score where Sno = '109' and Cno = '3-105') 20./* 理解1*/ 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 b where b.Cno = a.Cno) //每门课程的最高分 /*理解2*/ 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 ))//选修多门课程的同学中的最高分 21.select * from Score where Degree >(select Degree from Score where Sno = '109' and Cno = '3-105') 22.select Sno,Sname,Sbirthday from Student where YEAR(Sbirthday) = (select YEAR(Sbirthday) from Student where Sno = '108') 23.select * from Score where Cno in(select Cno from Course where Tno =(select Tno from Teacher where Tname='张旭')) 24.select Tname from Teacher where Tno in(select Tno from Course where Cno in(select Cno from Score group by Cno having count(*) > 5)) 25.select * from Student where Class in('95031','95033') 26.select distinct Cno from Score where Degree > 85 27.select * from Score where Cno in(select Cno from Course where Tno in(select Tno from Teacher where depart = '计算机系')) 28.select Tname,prof from Teacher where prof not in(select prof from Teacher where depart = '计算机系' and prof in(select prof from Teacher where depart='电子工程系' )) select prof from Teacher where depart = '计算机系' and prof not in(select prof from Teacher where depart='电子工程系' ) union select prof from Teacher where depart = '电子工程系' and prof not in(select prof from Teacher where depart='计算机系' ) 29.select * from Score where Cno='3-105' and Degree>any(select Degree from Score where Cno ='3-245') order by Degree desc 30.select * from Score where Cno='3-105' and Degree>all(select Degree from Score where Cno ='3-245') 31.select Sname,Ssex,Sbirthday from Student union select Tname,Tsex,Tbirthday from Teacher 32.select Sname,Ssex,Sbirthday from Student where Ssex='女' union select Tname,Tsex,Tbirthday from Teacher where Tsex='女' 33.select * from Score a where Degree<(select avg(Degree) from Score b where b.Cno = a.Cno) 34.select Tname,depart from Teacher where Tno in (select Tno from Course ) 成绩表上：select Tname,depart from Teacher where Tno in(select Tno from Course where Cno in(select Cno from Score)) 35.select Tname,depart from Teacher where Tno in(select Tno from Course where Cno not in(select Cno from Score) 36.select Class from Student where Ssex='男' group by Class having count(*)>1 37.select * from Student where Sno not in(select Sno from Student where Sname like '王%') 38.select Sname,YEAR(now())-YEAR(Sbirthday) from Student 39.select max(Sbirthday) from Student union select min(Sbirthday) from Student 40.select * from Student order by Class desc,Sbirthday 41.select * from Teacher join Course on Teacher.Tno = Course.Tno where Teacher.Tsex='男' 42.select * from Score where Degree = (select max(Degree) from Score ) 43.select Sname from Student where Ssex = (select Ssex from Student where Sname='李军') 44.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.select * from Score where Sno in(select Sno from Student where Ssex='男') and Cno in(select Cno from Course where Cname='计算机导论')
