MySQL45道面试题及答案

create database  school;
use school;

#学生表
create table `Student`
(
  `Sno` varchar(20) not null COMMENT '人名',
  `Sname` varchar(20) not null COMMENT '姓名',
  `Ssex` varchar(20) not null COMMENT '性别',
  `Sbirthday` datetime COMMENT '出生日期',
  `Class` varchar(20) COMMENT '班级'
);
#课程表
create table `Course`(
  `Cno` varchar(20) not null COMMENT '课程号',
  `Cname` varchar(20) not null COMMENT '课程名称',
  `Tno` varchar(20) not null COMMENT '教工编号'
);
#成绩表
Create table `Score` (
  `Sno` varchar(20) not null COMMENT '学号',
  `Cno` varchar(20) not NULL comment '课程号',
  `Degree` DECIMAL(4,1) null COMMENT '成绩'
);
#教师表
create table `Teacher` (
  `Tno` varchar(20) not null COMMENT '教工编号',
  `Tname` varchar(20) not null COMMENT '教工姓名',
  `Tsex` varchar(20) not null COMMENT '教工性别',
  `Tbirthday` datetime null COMMENT '教工出生日期',
  `Prof` varchar(20) null COMMENT '职称',
  `Depart` varchar(20) null COMMENT '教工所在部门'
);

insert into `Student` value
(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,'陆军','男','1974-06-03',95031);

insert into `Course` value
(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);

insert into `Score` value
(103,3-245,86),
(105,3-245,75),
(109,3-245,68),
(103,3-105,92),
(105,3-105,88),
(109,3-105,76),
(101,2-105,64),
(107,3-105,91),
(108,3-105,78),
(101,6-166,85),
(107,6-166,79),
(108,6-166,81);

insert into `Teacher` value
(804,'李城','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。
select `Sname`,`Ssex`,`Class` from `Student`;

#2、 查询教师所有的单位即不重复的Depart列。（多练）
select distinct Depart from `Teacher`;

-- 第三题 查询Student表的所有记录。
select * from `Student`;

-- 第四题 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;
select * from `Score` where Degree between 60 and 80;

-- 第五题 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);

-- 第六题 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';

-- 第七题 以Class降序查询Student表的所有记录。
select * from `Student` order by Class desc;

-- 第八题 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 ;

-- 第九题 查询“95031”班的学生人数。
select count(*) from `Student` where Class = '95031';

-- 第十题 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);
select Sno,Cno from `Score` order by Degree desc;

-- 第十一题 查询每门课的平均成绩。(group by:根据Cno进行分组)
select Cno,AVG(Degree) as 平均分 from `Score` group by Cno;

-- 第十二题 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 * from `Score` where Cno like '3%' group by Cno having Count(Cno)>4;

-- 第十三题 查询分数大于70，小于90的Sno列。
select Sno from `Score` where Degree>70 or Degree<90;
select Sno from `Score` where Degree between 70 and 90;

-- 第十四题 查询所有学生的Sname、Cno和Degree列。
select Sname,Cno from `Student` join `Score` on `Student`.Sno = `Score`.Sno;

-- 第十五题 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;

-- 第十六题 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`.Sno;

-- 第十七题 查询“95033”班学生的平均分。(子查询or条件查询)
select AVG(Degree) from  `Score` where Sno in(select Sno from `Student` where Class='95033');

select Avg(Degree) from `Score`,Student where Student.Sno = Score.Sno and Class = '95033';

-- 第十八题 假设使用如下命令建立了一个grade表：
create table `grede`(
  `low` int   COMMENT '人名',
  `upp` int not null COMMENT '课长',
  `rank` varchar(20) not null COMMENT '等级'
);
insert into `grede` values(90,100,'A');
insert into `grede` values(80,89,'B');
insert into `grede` values(70,79,'C');
insert into `grede` values(60,69,'D');
insert into `grede` values(0,59,'E');

-- 现查询所有同学的Sno、Cno和rank列。(between选取两个值之间的数据范围)
select Sno,Cno,Degree,rank from grede join Score on Score.Degree between
    low and upp;

select Sno,Cno,Degree,rank from  Score,grede where Degree between
    low and upp;

-- 第十九题 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 Score.Cno = '3-105' and Student.Sno = Score.Sno
and Score.Degree>(select Degree from Score where Cno = '3-105' and Sno = '109');

-- 第二十题 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 Degree<(select MAX(Degree)from  Score b
where a.Cno = b.Cno) and Sno in(select Sno from Score group by  Sno having  count(*) > 1);

-- 第二十一题 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 Student,Score where Student.Sno = Score.Sno and Score.Degree>
(select Degree from Score where Cno='3-105' and Sno = '109');

-- 第二十二题 查询和学号为107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 year(Student.Sbirthday) = (
    select year(Sbirthday) from student where Sno = '107'
    );

-- 第二十三题 查询“张旭“教师任课的学生成绩
select Sno,Cno,Degree from Score where Cno in(select Cno from Course where
   Tno in(select Tno from Teacher where Tname = '张旭'));

-- 第二十四题 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 where Cno in(select Cno from Score
group by Cno having Count(*)>5));

-- 第二十五题 查询95033班和95031班全体学生的记录。
select * from Student where Class = '95033' or Class = '95031';

-- 第二十六题 查询存在有85分以上成绩的课程Cno.
select distinct cno from Score where Degree>85;

-- 第二十七题 查询出“计算机系“教师所教课程的成绩表。
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'
    ));

-- 第二十八题查询“计算机系”与“电子工程系“不同职称的教师的Tname和Prof。使用相关子查询
select Tname,Prof from Teacher a where Prof not in(select Prof from Teacher b where
a.Depart!=b.Depart);

-- 第二十九题 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”课程的同学的Cno、Sno和Degree,并按Degree从高到低次序排序。
select Cno,Sno,Degree from Score a where (select Degree from Score b where Cno='3-105' and
b.Sno = a.Sno)>=(select Degree from Score c where Cno='3-245' and c.Sno = a.Sno)order by
Degree desc ;

-- 第三十题 查询选修编号为“3-105”课程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 a where (select Degree from Score b where Cno='3-105' and
b.Sno=a.Sno)>(select Degree from Score c where Cno='3-245' and c.Sno=a.Sno);

-- 第三十一题 查询所有教师和同学的name、sex和birthday.
select distinct Sname as name,Ssex as sex,Sbirthday as birthday from student
union
select distinct Tname as name,Tsex as sex,Tbirthday as birthday from Teacher;

-- 第三十二题 查询所有“女”教师和“女”同学的name、sex和birthday.
select distinct Sname as name,Ssex as sex,Sbirthday as birthday from student where Ssex = '女'
union
select distinct Tname as name,Tsex as sex,Tbirthday as birthday from Teacher where Tsex = '女';

-- 第三十三题 查询成绩比该课程平均成绩低的同学的成绩表。
select Sno,Cno,Degree from Score a where  a.Degree<(select AVG(Degree) from Score b where a.Cno = b.Cno);

-- 第三十四题 查询所有任课教师的Tname和Depart.
select Tname,Depart from Teacher where Tname in(select distinct Tname from Teacher,
Course,Score where Teacher.Tno = Course.Tno and Course.Cno = Score.Cno);

select Tname,Depart from Teacher where tno in (select tno from course where Cno in (select distinct Cno from Score));

-- 第三十五题 查询所有未讲课的教师的Tname和Depart.
select Tname,Depart from Teacher where Tname not in(select distinct Tname from Teacher,Course,Score where Teacher.Tno=Course.Tno and Course.Cno = Score.Cno);

-- 第三十六题 查询至少有2名男生的班号。
select Class from student where Ssex='男' group by Class having count(*)>1;

-- 第三十七题 查询Student表中不姓“王”的同学记录。
select * from Student where Sname not like ('王%');

-- 第三十八题 查询Student表中每个学生的姓名和年龄。
select Sname,YEAR(GETDATE())-year(Sbirthday) from student;

-- 第三十九题 查询Student表中最大和最小的Sbirthday日期值
select MAX(Sbirthday) as 最大,MIN(Sbirthday) as 最小 from student;

-- 第四十题 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 asc;

-- 第四十一题 查询“男”教师及其所上的课程。
select Tname,Cname from Teacher,Course where Tsex='男' and Teacher.Tno = Course.Tno;

-- 第四十二题 查询最高分同学的Sno、Cno和Degree列。
select Sno,Cno,Degree from Score where Degree=(select MAX(Degree) FROM score);

-- 第四十三题 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')and Sname
not in ('李军');

-- 第四十四题 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 Sname not in
('李军')and Class=(select Class from Student where Sname='李军');

-- 第四十五题 查询所有选修“计算机导论”课程的“男”同学的成绩表
select Sno,Degree 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');