数据库——练习题答案
create database 学生选课数据库
Create table Student
(
Sno Char(3) not null primary key, #学号
Sname Char(8) not null, #学生姓名
Ssex Char(2) not null, #学生姓名
Sbirthday datetime, #学生出生年月
Class Char(5) #学生所在班级
);
Create table Course
(
Cno Char(5) not null primary key, #课程号
Cname Varchar(10) not null, #课程名称
Tno Char(3) not null #教工编号
);
Create table Score
(
Sno Char(3) not null references Student(Sno) , #学号
Cno Char(5) not null references Course(Cno), #课程号
Degree Decimal(4,1) #成绩
);
create table Teacher
(
Tno Char(3) not null primary key, #教工编号
Tname Char(4) not null, #教工姓名
Tsex Char(2) not null, #教工性别
Tbirthday datetime, # 教工出生年月
Prof Char(6), #职称
Depart Varchar(10) not null #教工所在部门
);
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\');
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\');
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\');
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 between 60 and 80
5、 查询Score表中成绩为85，86或88的记录。
select * from Score where Degree=85 or Degree=86 or Degree=88
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=\'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, Degree desc
9、 查询“95031”班的学生人数。
select count(Sno) from Student where class=\'95031\'
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 Sno,Cno from Score where Degree=(select max(Degree) from Score)
11、 查询每门课的平均成绩。
select avg(Degree) from Score where Cno=\'3-245\';
select avg(Degree) from Score where Cno=\'3-105\';
select avg(Degree) from Score where Cno=\'6-166\';
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 group by Cno having count(Cno)>=5 and Cno like \'3%\'
select avg(Degree) from Score group by Cno having count(*)>=5 and Cno like \'3%\'
select avg(Degree) from Score where Cno like \'3%\' and Cno in (select Cno from Score 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 between 70 and 90
14、查询所有学生的Sname、Cno和Degree列。
select Student.Sname,Score.Cno,Score.Degree from Student,Score where
Student.Sno=Score.Sno
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 Score.Sno,Course.Cname,Score.Degree from Score,Course where Course.Cno=Score.Cno
select Sno,Cname,Degree from Score join Course on Course.Cno=Score.Cno
16、查询所有学生的Sname、Cname和Degree列。
select Student.Sname,Course.Cname,Score.Degree from Student,Course,Score where Student.Sno=Score.Sno and Course.Cno=Score.Cno
select Sname,Cname,Degree from Course join Score on Course.Cno=Score.Cno join Student on Student.Sno=Score.Sno
17、 查询“95033”班学生的平均分。
select avg(Degree) from Score,Student where Student.Sno=Score.Sno and class=\'95033\'
select avg(Degree) from Score where Sno in (select Sno from Student where class=\'95033\')
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
select Score.Sno,Score.Cno,grade.rank from score,grade where degree between low and upp #order by rank;
select Sno,Cno,rank from score join grade on degree between low and upp
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。
select * from Student,Score where Student.Sno=Score.Sno and Cno=\'3-105\' and Degree>76
select distinct a.Cno,a.Sno,a.Degree from Score a,Score b where a.Cno=\'3-105\' and a.Degree>b.Degree and b.Sno=\'109\' and b.Cno=\'3-105\'
select * from Score a where a.Cno=\'3-105\' and a.degree>(select degree b from Score where Sno=\'109\' and Cno=\'3-105\')
select * from Score where Cno=\'3-105\' and degree>(select degree from Score where Sno=\'109\' and Cno=\'3-105\')
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。
select Sno from Score group by Sno having count(*)>1;
select * from Score where Degree not in(select max(Degree) from Score group by cno) #非课程最高分
select * from Score a where Sno in(select Sno from Score group by Sno having count(*)>1) and
a.Degree not in (select max(Degree) from Score b where b.cno=a.cno) #非课程最高分
select * from Score where Sno in(select Sno from Score group by Sno having count(*)>1) and
Degree not in (select max(Degree) from Score group by sno)#非学号最高分
select * from Score where
Degree not in (select max(Degree) from Score group by sno having count(*)>1) and
Sno in(select Sno from Score group by Sno having count(*)>1)#非学号最高分
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。
select * from Score where degree>(select degree from Score where Sno=\'109\' and Cno=\'3-105\')
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。
select Sno,Sname,Sbirthday from Student where Sbirthday=(select Sbirthday from Student where Sno=\'108\') #年月日全部匹配
select Sno,Sname,Sbirthday from Student where Year(Sbirthday)=(select Year(Sbirthday) from Student where Sno=\'108\') #只匹配年
23、查询“张旭“教师任课的学生成绩。
select Degree from Score,Course,Teacher where Teacher.Tname=\'张旭\'and Teacher.Tno=Course.Tno and Course.Cno=Score.Cno
select Degree from Score where Cno=(select Cno from Course where Tno=(select Tno from Teacher where Tname=\'张旭\'))
24、查询选修某课程的同学人数多于5人的教师姓名。
select Tname from Teacher where Tno in (select Tno from Course,Score group by Score.Cno having count(Score.Cno)>5)
select Tname from Teacher where tno in(select tno from course where cno in (select cno from score group by cno having count(cno)>5))
25、查询95033班和95031班全体学生的记录。
select * from Student where class in(\'95033\',\'95031\')
26、查询存在有85分以上成绩的课程Cno.
select Cno from Score where Degree in (select Degree from Score group by Cno having Degree>85)
select distinct cno from score where degree>85
27、查询出“计算机系“教师所教课程的成绩表。
select distinct * from Score where Cno in (select Cno from Course where Tno in(select Tno from Teacher where Depart=\'计算机系\'))
select distinct Score.Sno,Score.Cno,Score.Degree from Score,Course,Teacher where Score.Cno=Course.Cno and Course.Tno=Teacher.Tno and Teacher.Depart=\'计算机系\'
28、查询“计算机系”与“电子工程系“不同职称的教师的Tname和Prof。
select Tname,Prof from Teacher where Depart=\'计算机系\' and prof not in (select Prof from Teacher where Depart=\'电子工程系\')
#只查出了计算机系中的记录
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\'))
#查出了计算机系和电子工程系的记录
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。
select Cno,Sno,Degree from Score where Cno=\'3-105\' and Degree>any (select Degree from Score where Cno=\'3-245\')order by Degree desc;
# any 任何一个值
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 Cno,Sno,Degree from Score where Cno=\'3-105\' and Degree>(select max(Degree) from Score where Cno=\'3-245\') order by Degree desc
select Cno,Sno,Degree from Score where Cno=\'3-105\' and Degree>all(select Degree from Score where Cno=\'3-245\') #all 所有值
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,Tsex,Tbirthday from Teacher where Tsex=\'女\' union select Sname,Ssex,Sbirthday from Student where Ssex=\'女\'
33、 查询成绩比该课程平均成绩低的同学的成绩表。
select * from Score a where a.Degree<(select avg(Degree) from Score b where b.Cno=a.Cno)
34、 查询所有任课教师的Tname和Depart.
select Tname,Depart from Teacher
select Tname,Depart from Teacher where Tno in(select Tno from Course where Teacher.Tno=Course.Tno) #理解为有课就有任课
select Tname,Depart from Teacher where exists(select Tno from Course where Teacher.Tno=Course.Tno) #通常用exists里面select后面跟*
select Tname,Depart from Teacher where Tno in(select tno from course where cno in (select cno from score where cno !=0))#理解为有课并有学生选课才是有任课
select Tname,Depart from Teacher where Tno in(select tno from course where cno in (select cno from score where course.cno=score.cno))#理解为有课并有学生选课才是有任课
35 、 查询所有未讲课的教师的Tname和Depart.
select Tname,Depart from Teacher where Tno not in(select Tno from Course)
select Tname,Depart from Teacher where not exists(select Tno from Course where Teacher.Tno=Course.Tno) #通常用exists里面select后面跟*
select Tname,Depart from Teacher where Tno not in(select tno from course where cno in (select cno from score where cno !=0))
select Tname,Depart from Teacher where Tno not in(select tno from course where cno in (select cno from score))
36、查询至少有2名男生的班号。
select class from Student where Ssex=\'男\' group by class having count(Student.Ssex)>=2
select class from Student where Ssex=\'男\' group by class having count(*)>=2
37、查询Student表中不姓“王”的同学记录。
select * from Student where Sname not like \'王%\'
38、查询Student表中每个学生的姓名和年龄。
select Sname as 姓名,year(now())-year(Sbirthday) as 年龄 from Student
#now sysdate 取现在的时间，年月日点
39、查询Student表中最大和最小的Sbirthday日期值。
select max(Sbirthday),min(Sbirthday) from Student
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
41、查询“男”教师及其所上的课程。
select Teacher.Tname,Teacher.Tsex,Course.Cname from Teacher,Course where Teacher.Tsex=\'男\' and Teacher.Tno=Course.Tno
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 * from Score where Degree=(select max(Degree) from Score)
43、查询和“李军”同性别的所有同学的Sname.
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 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\'#fen
select Sno from Student where Ssex=\'男\' #fen
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\')
#满足一个条件可以用‘=’，满足多个条件用‘in’，所以最好都用‘in’