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Mysql 综述三部曲的综合练习（1）看看自己水平能达到面试水准吗？

时间：2024-06-09 23:00:24浏览次数：13  
标签：综述 Cid 三部曲 Mysql score Student Sid SC where

Mysql综合练习

数据库表信息

Student(Sid,Sname,Sage,Ssex) 学生表——Sid：学号；Sname：学生姓名；Sage：学生年龄；Ssex：学生性别

Course(Cid,Cname,Tid) 课程表——Cid：课程编号；Cname：课程名字；Tid：教师编号

SC(Sid,Cid,score) 成绩表——Sid：学号；Cid：课程编号；score：成绩

Teacher(Tid,Tname) 教师表——Tid：教师编号； Tname：教师名字

创建数据库表

       这里我自己创建数据表，如果你们刚学完MySQL可以自己试着创建，数据类型最好不要随便用，够用就行，减少内存的占用。
       数据表可以添加数据方便实战，也可以不添加数据直接敲出代码。
       给表命名可能都不一样，能得出问题的答案就行。
       题目总共50道，有把握全对吗？

-- Courses 数据表
create table Course (
   Cid                   bigint not null comment '课程编号',
   Cname                 varchar(32) comment '课程名字',
   Tid                   bigint comment '教师编号',
   primary key (Cid)
)ENGINE = InnoDB
DEFAULT CHARACTER SET = utf8;

-- SC 数据表
 create table SC (
   Sid                   bigint not null comment '学号',
   Cid                   bigint comment '课程编号',
   score                 int comment '成绩',
   primary key (Sid)
)ENGINE = InnoDB
DEFAULT CHARACTER SET = utf8;

-- Student 数据表
create table Student (
   Sid                  bigint not null comment '学号',
   Sname                varchar(32) comment '学生姓名',
   Sage                 int comment '学生年龄',
   Ssex                 varchar(10) comment '学生性别',
   primary key (Sid)
)ENGINE = InnoDB
DEFAULT CHARACTER SET = utf8;

-- Teacher 数据表
create table Teacher (
   Tid                  bigint not null comment '教师编号',
   Tname                varchar(32) comment '教师名字',
   primary key (Tid)
)ENGINE = InnoDB
DEFAULT CHARACTER SET = utf8;

综合练习（含答案）

1、查询1课程比2课程成绩高的所有学生的学号

select a.Sid 
from (select Sid,score from SC where Cid = 1) a,(select Sid,score
from SC where Cid = 2) b
where a.score > b.score and a.Sid = b.Sid;

2、查询平均成绩大于70分的同学的学号和平均成绩

select Sid,avg(score)
from SC
group by Sid having avg(score) > 70;

3、查询所有同学的学号、姓名、选课数、总成绩

select Student.Sid,Student.Sname,count(SC.Cid),sum(score)
from Student 
left Outer join SC on Student.Sid = SC.Sid
group by Student.Sid,Sname;

4、查询姓“王”的老师的个数

select count(distinct(Tname))
from Teacher
where Tname like '王%';

5、查询没学过“王先生”老师课的同学的学号、姓名

select Student.Sid,Student.Sname
from Student
where Sid not in 
(select distinct(SC.Sid) 
from SC,Course,Teacher where SC.Cid = Course.Cid and Teacher.Tid = Course.Tid and Teacher.Tname = '王先生');

6、查询学过1并且也学过编号2课程的同学的学号、姓名

select Student.Sid,Student.Sname 
from Student,SC 
where Student.Sid = SC.Sid and SC.Cid = 1 and exists
(Select * from SC as SC_2 
where SC_2.Sid = SC.Sid and SC_2.Cid = 2);

7、查询学过“王先生”老师所教的所有课的同学的学号、姓名

select Sid,Sname
from Student
where Sid in 
(select Sid from SC ,Course ,Teacher where SC.Cid = Course.Cid and Teacher.Tid = Course.Tid and
Teacher.Tname = '王先生'
group by Sid having count(SC.Cid) = (select count(Cid) 
from Course,Teacher where
Teacher.Tid = Course.Tid and Tname = '王先生'));

8、查询课程编号2的成绩比课程编号1课程低的所有同学的学号、姓名

Select Sid,Sname 
from (select Student.Sid,Student.Sname,score,
(select score from SC SC_2 where SC_2.Sid = Student.Sid
and SC_2.Cid = 2) score2
from Student,SC 
where Student.Sid=SC.Sid and Cid = 1) S_2 
where score2 < score;

9、查询所有课程成绩小于70分的同学的学号、姓名

select Sid,Sname
from Student
where Sid not in (select Student.Sid from Student,SC where S.Sid = SC.Sid and score > 70);

10、查询没有学全所有课的同学的学号、姓名

select Student.Sid,Student.Sname
from Student,SC
where Student.Sid=SC.Sid group by Student.Sid,Student.Sname having count(Cid) < (select count(Cid) from Course);

11、查询至少有一门课与学号为“1”的同学所学相同的同学的学号和姓名

select Sid,Sname from Student,SC where Student.Sid = SC.Sid and Cid in select Cid from SC where Sid = 1;

12、查询至少学过学号为1同学所有一门课的其他同学学号和姓名

select distinct SC.Sid,Sname
from Student,SC
where Student.Sid = SC.Sid and Cid in (select Cid from SC where Sid = 1);

13、把“SC”表中“王先生”老师教的课的成绩都更改为此课程的平均成绩

update SC set score = (select avg(SC_2.score)
from SC SC_2
where SC_2.Cid=SC.Cid) from Course,Teacher where Course.Cid = SC.Cid and Course.Tid=Teacher.Tid and Teacher.Tname = '王先生');

14、查询和“1”号的同学学习的课程完全相同的其他同学学号和姓名

select Sid 
from SC 
where Cid in 
(select Cid from SC where Sid = 12)
group by Sid having count(*) = (select count(*) from SC where Sid = 1);

15、删除学习“王先生”老师课的SC表记录

Delect SC
from course ,Teacher
where Course.Cid = SC.Cid and Course.Tid= Teacher.Tid and Tname = '王先生';

15、查询含有姓名“先”的老师的个数

select count(distinct(Tname))
from Teacher
where Tname like '%王%';

17、按平均成绩从高到低显示所有学生的“数据库”、“企业管理”、“英语”三门的课程成绩，按如下形式显示： 学生ID,数据库,企
业管理,英语,有效课程数,有效平均分

SELECT Sid as 学生ID
,(SELECT score FROM SC WHERE SC.Sid=t.Sid AND Cid = 4) AS 数据库
,(SELECT score FROM SC WHERE SC.Sid=t.Sid AND Cid = 1) AS 企业管理
,(SELECT score FROM SC WHERE SC.Sid=t.Sid AND Cid = 006) AS 英语
,COUNT(*) AS 有效课程数, AVG(t.score) AS 平均成绩
FROM SC AS t
GROUP BY Sid
ORDER BY avg(t.score);

18、查询各科成绩最高和最低的分：以如下形式显示：课程ID，最高分，最低分

SELECT L.Cid As 课程ID,L.score AS 最高分,R.score AS 最低分
FROM SC L ,SC AS R
WHERE L.Cid = R.Cid and
L.score = (SELECT MAX(IL.score)
FROM SC AS IL,Student AS IM
WHERE L.Cid = IL.Cid and IM.Sid=IL.Sid
GROUP BY IL.Cid)
AND
R.score = (SELECT MIN(IR.score)
FROM SC AS IR
WHERE R.Cid = IR.Cid
GROUP BY IR.Cid);

19、按各科平均成绩从低到高和及格率的百分数从高到低顺序

SELECT t.Cid AS 课程号,max(course.Cname)AS 课程名,isnull(AVG(score),0) AS 平均成绩
,100 * SUM(CASE WHEN isnull(score,0) >= 60 THEN 1 ELSE 0 END) / COUNT(*) AS 及格百分数
FROM SC T,Course
where t.Cid = course.Cid
GROUP BY t.Cid
ORDER BY 100 * SUM(CASE WHEN isnull(score,0) >= 60 THEN 1 ELSE 0 END) / COUNT(*) DESC

20、查询如下课程平均成绩和及格率的百分数(用”1行”显示): 企业管理（1），马克思（2），OO&UML （3），数据库（4）

SELECT SUM(CASE WHEN Cid = 1 THEN score ELSE 0 END) / SUM(CASE Cid WHEN ‘1’ THEN 1 ELSE 0 END) AS 企业管理平均分
,100 * SUM(CASE WHEN Cid = 1 AND score >= 60 THEN 1 ELSE 0 END) / SUM(CASE WHEN Cid = 1 THEN 1 ELSE 0 END)
AS 企业管理及格百分数
,SUM(CASE WHEN Cid = 2 THEN score ELSE 0 END) / SUM(CASE Cid WHEN 2 THEN 1 ELSE 0 END) AS 马克思平均分
,100 * SUM(CASE WHEN Cid = 2 AND score >= 60 THEN 1 ELSE 0 END) / SUM(CASE WHEN Cid = 2 THEN 1 ELSE 0 END)
AS 马克思及格百分数
,SUM(CASE WHEN Cid = 3 THEN score ELSE 0 END)/SUM(CASE Cid WHEN 3 THEN 1 ELSE 0 END) AS UML平均分
,100 * SUM(CASE WHEN Cid = 3 AND score >= 60 THEN 1 ELSE 0 END) / SUM(CASE WHEN Cid = 3 THEN 1 ELSE 0 END)
AS UML及格百分数
,SUM(CASE WHEN Cid = 4 THEN score ELSE 0 END) / SUM(CASE Cid WHEN 4 THEN 1 ELSE 0 END) AS 数据库平均分
,100 * SUM(CASE WHEN Cid = 4 AND score >= 60 THEN 1 ELSE 0 END) / SUM(CASE WHEN Cid = 4 THEN 1 ELSE 0 END)
AS 数据库及格百分数
FROM SC

21、查询不同老师所教不同课程平均分从高到低显示

SELECT max(Z.Tid) AS 教师ID,MAX(Z.Tname) AS 教师姓名,C.Cid AS 课程ID,MAX(C.Cname) AS 课程名称,AVG(Score) AS 平均成绩
FROM SC AS T,Course AS C ,Teacher AS Z
where T.Cid = C.Cid and C.Tid = Z.Tid
GROUP BY C.Cid
ORDER BY AVG(Score) DESC;

22、查询如下课程成绩第 3 名到第 6 名的学生成绩单：企业管理（1），马克思（2），UML （3），数据库（4）。
打印：[学生ID],[学生姓名],企业管理,马克思,UML,数据库,平均成绩

SELECT DISTINCT top 3
SC.Sid As 学生学号,
Student.Sname AS 学生姓名 ,
T1.score AS 企业管理,
T2.score AS 马克思,
T3.score AS UML,
T4.score AS 数据库,
ISNULL(T1.score,0) + ISNULL(T2.score,0) + ISNULL(T3.score,0) + ISNULL(T4.score,0) as 总分
FROM Student,SC LEFT JOIN SC AS T1
ON SC.Sid = T1.Sid AND T1.Cid = 1
LEFT JOIN SC AS T2
ON SC.Sid = T2.Sid AND T2.Cid = 2
LEFT JOIN SC AS T3
ON SC.Sid = T3.Sid AND T3.Cid = 3
LEFT JOIN SC AS T4
ON SC.Sid = T4.Sid AND T4.Cid = 4
WHERE student.Sid=SC.Sid and
ISNULL(T1.score,0) + ISNULL(T2.score,0) + ISNULL(T3.score,0) + ISNULL(T4.score,0)
NOT IN
(SELECT
DISTINCT
TOP 15 WITH TIES
ISNULL(T1.score,0) + ISNULL(T2.score,0) + ISNULL(T3.score,0) + ISNULL(T4.score,0)
FROM sc
LEFT JOIN sc AS T1
ON sc.Sid = T1.Sid AND T1.Cid = k1
LEFT JOIN sc AS T2
ON sc.Sid = T2.Sid AND T2.Cid = k2
LEFT JOIN sc AS T3
ON sc.Sid = T3.Sid AND T3.Cid = k3
LEFT JOIN sc AS T4
ON sc.Sid = T4.Sid AND T4.Cid = k4
ORDER BY ISNULL(T1.score,0) + ISNULL(T2.score,0) + ISNULL(T3.score,0) + ISNULL(T4.score,0) DESC);

23、统计列印各科成绩,各分数段人数:课程ID,课程名称,[100-85],[85-70],[70-60],[ <60]

SELECT SC.Cid as 课程ID, Cname as 课程名称,
SUM(CASE WHEN score BETWEEN 85 AND 100 THEN 1 ELSE 0 END) AS [100 – 85],
SUM(CASE WHEN score BETWEEN 70 AND 85 THEN 1 ELSE 0 END) AS [85 – 70],
SUM(CASE WHEN score BETWEEN 60 AND 70 THEN 1 ELSE 0 END) AS [70 – 60],
SUM(CASE WHEN score < 60 THEN 1 ELSE 0 END) AS [60 -],
FROM SC,Course
where SC.Cid=Course.Cid
GROUP BY SC.Cid,Cname;

24、查询学生平均成绩及其名次

SELECT 1 + (SELECT COUNT( distinct 平均成绩)
FROM (SELECT Sid,AVG(score) AS 平均成绩
FROM SC
GROUP BY Sid
) AS T1
WHERE 平均成绩 > T2.平均成绩) as 名次,
Sid as 学生学号,平均成绩
FROM (SELECT Sid,AVG(score) 平均成绩
FROM SC
GROUP BY Sid
) AS T2
ORDER BY 平均成绩 desc;

25、查询各科成绩前三名的记录:(不考虑成绩并列情况)

SELECT t1.Sid as 学生ID,t1.Cid as 课程ID,score as 分数
FROM SC t1
WHERE score IN (SELECT TOP 3 score
FROM SC
WHERE t1.Cid= Cid
ORDER BY score DESC
)
ORDER BY t1.Cid;

26、查询每门课程被选修的学生数

select Cid,count(Sid) from SC group by Cid;

27、查询出只选修了一门课程的全部学生的学号和姓名

select SC.Sid,Student.Sname,count(Cid) AS 选课数
from SC ,Student
where SC.Sid = Student.Sid group by SC.Sid ,Student.Sname having count(Cid) = 1;

28、查询男生、女生人数

Select count(Ssex) as 男生人数 from Student group by Ssex having Ssex='男';
Select count(Ssex) as 女生人数 from Student group by Ssex having Ssex='女';

29、查询姓“王”的学生名单

SELECT Sname FROM Student WHERE Sname like '王%';

30、查询同名同性学生名单，并统计同名人数

select Sname,count(*) from Student group by Sname having count(*) > 1;

31、1555年出生的学生名单(注：Student表中Sage列的类型是datetime)

select Sname, CONVERT(char (11),DATEPART(year,Sage)) as age
from Student
where CONVERT(char(11),DATEPART(year,Sage) )= '1555';

32、查询每门课程的平均成绩，结果按平均成绩升序排列，平均成绩相同时，按课程号降序排列

Select Cid,Avg(score) from SC group by Cid order by Avg(score),Cid DESC ;

33、查询平均成绩大于90的所有学生的学号、姓名和平均成绩

select Sname,SC.Sid ,avg(score)
from Student,SC
where Student.Sid = SC.Sid group by SC.Sid,Sname having avg(score) > 90;

34、查询课程名称为“数据库”，且分数低于50的学生姓名和分数

Select Sname,isnull(score,0)
from Student,SC,Course
where SC.Sid = Student.Sid and SC.Cid = Course.Cid and Course.Cname= '数据库' and score < 50;

35、查询所有学生的选课情况；

SELECT SC.Sid,SC.Cid,Sname,Cname
FROM SC,Student,Course
where SC.Sid = Student.Sid and SC.Cid = Course.Cid ;

36、查询任何一门课程成绩在70分以上的姓名、课程名称和分数；

SELECT distinct Student.Sid,Student.Sname,SC.Cid,SC.score
FROM Student,Sc
WHERE SC.score>=70 AND SC.Sid = Student.Sid;

37、查询不及格的课程，并按课程号从大到小排列

select Cid from SC where score < 60 order by Cid ;

38、查询课程编号为3且课程成绩在80分以上的学生的学号和姓名；

select SC.Sid,Student.Sname from SC,Student where SC.Sid = Student.Sid and Score > 80 and Cid = 3;

39、求选了课程的学生人数

select count(*) from SC;

40、查询选修“王先生”老师所授课程的学生中，成绩最高的学生姓名及其成绩

select Student.Sname,score
from Student,SC,Course C,Teacher
where Student.Sid = SC.Sid and SC.Cid = C.Cid and C.Tid = Teacher.Tid and Teacher.Tname='王先生' and SC.score = (select max
(score)from SC where Cid = C.Cid );

41、查询各个课程及相应的选修人数

select count(*) from SC group by Cid;

42、查询不同课程成绩相同的学生的学号、课程号、学生成绩

select distinct A.Sid,B.score 
from SC A ,SC B 
where A.score = B.score and A.Cid <> B.Cid ;

43、查询每门功成绩最好的前两名

SELECT t1.Sid as 学生ID,t1.Cid as 课程ID,score as 分数
FROM SC t1
WHERE score IN (SELECT TOP 2 score
FROM SC
WHERE t1.Cid= Cid
ORDER BY score DESC
)
ORDER BY t1.Cid;

44、统计每门课程的学生选修人数（超过10人的课程才统计）。要求输出课程号和选修人数，查询结果按人数降序排列，查询结果按人数
降序排列，若人数相同，按课程号升序排列

select Cid as 课程号,count(*) as 人数
from SC
group by Cid
order by count(*) desc,Cid

45、检索至少选修两门课程的学生学号

select Sid
from SC
group by Sid
having count(*) > = 2

46、查询全部学生都选修的课程的课程号和课程名

select Cid,Cname
from Course
where Cid in (select Cid from SC group by Cid)

47、查询没学过“王先生”老师讲授的任一门课程的学生姓名

select Sname 
from Student where Sid not in (select Sid from Course,Teacher,SC 
where Course.Tid = Teacher.Tid and
SC.Cid = course.Cid and Tname = '王先生');

48、查询两门以上不及格课程的同学的学号及其平均成绩

select Sid,avg(isnull(score,0)) from SC where Sid in (select Sid from SC where score < 60 group by Sid having count
(*) > 2)group by Sid;

49、检索“4”课程分数小于60，按分数降序排列的同学学号

select Sid from SC where Cid = 4 and score < 60 order by score desc;

50、删除2同学的1课程的成绩

delete from SC where Sid = 2 and Cid = 1;

标签：综述,Cid,三部曲,Mysql,score,Student,Sid,SC,where
From： https://blog.csdn.net/weixin_48261123/article/details/139529448

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