数据分析-SQL练习

时间 2019-11-20

标签数据分析 sql 练习栏目 SQL 繁體版

原文原文链接

图片、部分试题来源网络，侵删，谢谢。html

1.SQL 45题

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','操做系统',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表中的全部记录的Sname、Ssex和Class列

select Sname, Ssex, Class from student;

2 查询教师全部的单位即不重复的Depart列。（多练）

select distinct depart from teacher;

3 查询Student表的全部记录

select * from student;

4 查询Score表中成绩在60到80之间的全部记录

select Sno, Cno, degree 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 Sno, Cno, degree from score where degree = 85 or degree = 86 or degree = 88;
#或另外一种写法
select * from score where degree in (85, 86, 88)

6 查询Student表中“95031”班或性别为“女”的同窗记录

select * from student where Class = '95031' or Ssex = '女';

7 以Class降序查询Student表的全部记录

select * from student order by Class desc;

8 以Cno升序、Degree降序查询Score表的全部记录

select * from score order by Cno asc, degree desc;
# asc, ascending order(升序排列）, desc, descending order(降序排列）, 默认按升序排列

9 查询“95031”班的学生人数

select count(Class) as '95031班学生数'  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 * from score where degree = (select max(degree) from score); 
# 直接写 select * from score where degree = max(degree)不行，会报错

11 查询每门课的平均成绩。(group by:根据Cno进行分组) *

select Cno, avg(degree) as '课程平均分' from score group by Cno ;

12 查询Score表中至少有4名学生选修的并以3开头的课程的平均分数(须要细究）

select cno, avg(degree) from score where cno like '3%' group by cno having count(sno) > 4;
#参考网站是5名学生，则查询不到，应为4名学生
#like '3%' 以3开头，或like '%3' 以3结尾, 或包含'%12%'\
#HAVING增长的缘由是WHERE关键字没法与合计函数一块儿使用

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 查询全部学生的Sname、Cno和Degree列

select student.Sname, score.Cno, score.Degree from student, score where student.Sno = score.Sno;
#另外一种inner join 写法
select student.Sname, score.Cno, score.Degree from student inner join score on student.Sno = score.Sno

15 查询全部学生的Sno、Cname和Degree列

select score.Sno, course.Cname, score.Degree from  score, course where course.Cno = score.Cno;
#或另外一种inner join写法
select score.Sno, course.Cname, score.Degree from  score INNER JOIN course on course.Cno = score.Cno;

16 查询全部学生的Sname、Cname和Degree列

select student.Sname, course.Cname, score.Degree from student, course, score WHERE student.Sno = score.Sno and score.Cno = course.Cno;

17 查询“95033”班学生的平均分。(子查询or条件查询)

select avg(degree) as '95033班平均分' from score where sno in (select sno from student where Class = '95033');

18 假设使用以下命令创建了一个grade表

create table `grade`( `low` int COMMENT '人名', `upp` int not null COMMENT '课长', `weight` varchar(20) not null COMMENT '等级' ); 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');
#网络上的grede，错误, rank关键字不能用，sql存在rank函数,经测试更改成weight能够

19 现查询全部同窗的Sno、Cno和weight列。(between选取两个值之间的数据范围)

#select Sno,Cno,Degree,rank from grade join Score on Score.Degree between low and upp;
#select Sno,Cno,Degree,rank from Score, grade where Degree between low and upp;
以上为网络上的答案，在Navicat 11.1.13测试错误，实际也是由于rank关键字的缘由

select Sno, Cno, weight from Score, grade where (score.Degree > grade.low and score.Degree < grade.upp);
或者是
select Sno, Cno, weight from Score, grade where Degree between low and upp;
或者是
select Sno, Cno, weight from Score inner join grade where Degree between low and upp

20 查询选修“3-105”课程的成绩高于“109”号同窗成绩的全部同窗的记录

select sno from score where score.cno = '3-105' and score.degree>(select Degree from Score where Cno = '3-105' and Sno = '109');
#上面是个人答案，题目要求是查询到全部同窗的记录，我的是把全部的同窗找出来了，下面是网络上的答案，把知足条件的同窗的特征又补全了。
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');

21 查询score中选学多门课程的同窗中分数为非最高分红绩的记录(挺难）

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);

22 查询成绩高于学号为“109”、课程号为“3-105”的成绩的全部记录

select * from Student,Score where Student.Sno = Score.Sno and Score.Degree>
(select Degree from Score where Cno='3-105' and Sno = '109');
#此为网络上答案，我的感受不对，第一要求只查询课程号3-105的课程，实际查询少限制条件，第二信息不全
select * from student, course, score where score.sno = student.sno and score.cno = course.cno and score.cno = '3-105' and score.degree > 
(select degree from score where cno = '3-105' and sno = '109')

23 查询和学号为107的同窗同年出生的全部学生的Sno、Sname和Sbirthday列

select Sno, Sname, Sbirthday from student where YEAR(Sbirthday) = (select year(Sbirthday) from student where sno = '107');
#用到了year()函数

24 查询“张旭“教师任课的学生成绩

select * from student, course, score where student.sno =score.sno and score.cno = course.cno and course.tno = (select tno from teacher where tname = '张旭');
#以上为个人答案，将学生的信息补充的较为完整，如下是网络答案，两个where in 跟score.cno = course.cno student.sno = score.sno 等价，也是另外一种写法
select Sno,Cno,Degree from Score where Cno in(select Cno from Course where Tno in(select Tno from Teacher where Tname = '张旭'));

25 查询选修某课程的同窗人数多于5人的教师姓名

select DISTINCT tname from teacher where tno in (select tno from course where cno in (select cno from score group by cno having count(sno) > 5));
#以前的联等的写法行不通，由于没想到group by 与having count和where之间的链接方式

26 查询95033班和95031班全体学生的记录

select * from student where Class='95033' or Class='95031'

27 查询存在有85分以上成绩的课程Cno

select cno from score where degree >= 85;

28 查询出“计算机系“教师所教课程的成绩表

select * from teacher, student, course, score where score. sno = student.sno and score.cno = course.cno and teacher.tno =course.tno and teacher.depart = '计算机系';
#此处有歧义的是成绩表到底包含哪些内容，一般学生姓名、性别、学号包含，因此这里我把信息特征补的较为齐全
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'))
#以上为网络答案

29 查询“计算机系”与“电子工程系“不一样职称的教师的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);
#此处感受略奇怪，不一样职称的应该有遗漏

30 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”课程的同窗的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 ;

31 查询选修编号为“3-105”课程且成绩高于选修编号为“3-245”课程的同窗的Cno、Sno和Degree.

select cno, sno, degree from score a where (select degree from score b where cno = '3-105' and a.sno = b.sno) > (select degree from score c where cno = '3-245' and a.sno = c.sno);

32 查询全部教师和同窗的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 （ORDER BY birthday） ;
#这里order by birthday 是本身加的，按生日升序排列，实际不用

33 查询全部“女”教师和“女”同窗的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';

34 查询成绩比该课程平均成绩低的同窗的成绩表

SELECT sno, cno, degree from score a  where a.degree < (select avg(Degree) from score b where a.sno = b.sno);

35 查询全部任课教师的Tname和Depart

select tname, depart from teacher where tname in (select distinct tname from teacher, course, score, student where course.tno = teacher.tno and course.cno = score.cno and score.sno =student.sno);

36 查询全部未讲课的教师的Tname和Depart

select tname, depart from teacher where tname not in (select distinct tname from teacher, course, score, student where course.tno = teacher.tno and course.cno = score.cno and score.sno =student.sno);

37 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;

38 查询Student表中不姓“王”的同窗记录

select * from Student where Sname not like ('王%');

39 查询Student表中每一个学生的姓名和年龄（暂有问题）

select Sname,YEAR(GETDATE())-year(Sbirthday) from student;
#getdate函数不可用

40 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;

41 以班号和年龄从大到小的顺序查询Student表中的所有记录

select * from Student order by Class desc ,Sbirthday asc;
#注意生日数字越大，年龄越小

42 查询“男”教师及其所上的课程

select Tname,Cname from Teacher,Course where teacher.Tsex='男' and Teacher.Tno = Course.Tno;

43 查询最高分同窗的Sno、Cno和Degree列

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

44 查询和“李军”同性别的全部同窗的Sname.

select sname from student where ssex = (select ssex from student where sname = '李军') and sname not in ('李军');

45 查询和“李军”同性别并同班的同窗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');

46 查询全部选修“计算机导论”课程的“男”同窗的成绩表

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')；

2. SQL 面试题

2.1 row_number

2.2 行列转换

id    学生姓名    课程名称    课程成绩
1    张三         Linux       85
2    张三         MySQL       92
3    张三         Java        87
4    李四         Linux       96
5    李四         MySQL       100
7    王五         Linux       91
8    王五         MySQL       83
9    王五         Java        98

学生姓名    Linux    MySQL    Java
张三          85      92      87
李四          96      89      100
王五          91      83      98

#建立数据表
CREATE TABLE tb_lemon_grade (
id INT(10) NOT NULL AUTO_INCREMENT PRIMARY KEY,
student_name VARCHAR(20) DEFAULT NULL,
course VARCHAR(20) DEFAULT NULL,
score FLOAT DEFAULT '0');
#更改显示形式
SELECT  student_name,
MAX(IF(COURSE = 'Linux',SCORE,0)) 'Linux',
MAX(IF(COURSE = 'MySQL',SCORE,0)) 'MySQL',
MAX(IF(COURSE = 'Java',SCORE,0)) 'Java'
FROM lemon_grade
group by student_name;

year   month amount
1991   1     1.1
1991   2     1.2
1991   3     1.3
1991   4     1.4
1992   1     2.1
1992   2     2.2
1992   3     2.3
1992   4     2.4

year m1   m2   m3   m4
1991 1.1 1.2 1.3 1.4
1992 2.1 2.2 2.3 2.4 

select year, 
(select amount from   aaa m where month=1   and m.year=aaa.year) as m1,
(select amount from   aaa m where month=2   and m.year=aaa.year) as m2,
(select amount from   aaa m where month=3   and m.year=aaa.year) as m3,
(select amount from   aaa m where month=4   and m.year=aaa.year) as m4
from aaa   group by year

 姓名  类别          花费
  李  看电影         30
  李  吃饭           100
  李  旅游           500
  王  吃饭           500
  王  看电影         100
  王  买衣服         700

姓名     TOP1类别        TOP1花费         TOP2类别       TOP2花费            TOP3类别         TOP3花费
李       旅游            500               吃饭            100               看电影            30
王       买衣服          700               吃饭            500               看电影            100

#decode(条件,值1,翻译值1,值2,翻译值2,...值n,翻译值n,缺省值)

2.3 索引

索引就一种特殊的查询表，数据库的搜索引擎能够利用它加速对数据的检索。它很相似与现实生活中书的目录，不须要查询整本书内容就能够找到想要的数据。索引能够是惟一的，建立索引容许指定单个列或者是多个列。缺点是它减慢了数据录入的速度，同时也增长了数据库的尺寸大小。git

2.4 union all 与 union 的区别

union 去重且排序， union all 不去重且不排序github

2.5 where 和 having 的区别

WHERE 子句用来筛选 FROM 子句中指定的操做所产生的行。GROUP BY 子句用来分组 WHERE 子句的输出。HAVING 子句用来从分组的结果中筛选行面试

2.6 经常使用的时间函数

经常使用的日期提取函数包括 year()/month()/day()/hour()/minute()/second()sql

日期运算函数包括datediff(enddate,startdate) 计算两个时间的时间差（day)；数据库

date_sub(startdate,days) 返回开始日期startdate减小days天后的日期。网络

date_add(startdate,days) 返回开始日期startdate增长days天后的日期。模块化

2.7 存储过程

存储过程是一个预编译的 SQL 语句，优势是容许模块化的设计，就是说只需建立一次，之后在该程序中就能够调用屡次。若是某次操做须要执行屡次 SQL ，使用存储过程比单纯 SQL 语句执行要快。能够用一个命令对象来调用存储过程。函数

create proc StuProc
@sname varchar(100)   
as 
begin
select S#,Sname,Sage,Ssex from student where sname=@sname
end
go

2.8 要求给定数据展现效果

2.9 分组函数使用

2.10 LEFT JOIN、RIGHT JOIN、INNER JOIN、FULL JOIN

2.11 查询某时间段例如0:00-9:00用户登陆次数。

给定user_id, login_time(时间戳)，表A测试