SQL笔试 I 经典44题及答案解析~

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今天这篇文章，是关于44道经典SQL测试题：

01 建表语句

create table Student(sid varchar(10),sname varchar(10),sage datetime,ssex nvarchar(10));insert into Student values('01' , '赵雷' , '1990-01-01' , '男');insert into Student values('02' , '钱电' , '1990-12-21' , '男');insert into Student values('03' , '孙风' , '1990-05-20' , '男');insert into Student values('04' , '李云' , '1990-08-06' , '男');insert into Student values('05' , '周梅' , '1991-12-01' , '女');insert into Student values('06' , '吴兰' , '1992-03-01' , '女');insert into Student values('07' , '郑竹' , '1989-07-01' , '女');insert into Student values('08' , '王菊' , '1990-01-20' , '女');create table Course(cid varchar(10),cname varchar(10),tid varchar(10));insert into Course values('01' , '语文' , '02');insert into Course values('02' , '数学' , '01');insert into Course values('03' , '英语' , '03');create table Teacher(tid varchar(10),tname varchar(10));insert into Teacher values('01' , '张三');insert into Teacher values('02' , '李四');insert into Teacher values('03' , '王五');create table SC(sid varchar(10),cid varchar(10),score decimal(18,1));insert into SC values('01' , '01' , 80);insert into SC values('01' , '02' , 90);insert into SC values('01' , '03' , 99);insert into SC values('02' , '01' , 70);insert into SC values('02' , '02' , 60);insert into SC values('02' , '03' , 80);insert into SC values('03' , '01' , 80);insert into SC values('03' , '02' , 80);insert into SC values('03' , '03' , 80);insert into SC values('04' , '01' , 50);insert into SC values('04' , '02' , 30);insert into SC values('04' , '03' , 20);insert into SC values('05' , '01' , 76);insert into SC values('05' , '02' , 87);insert into SC values('06' , '01' , 31);insert into SC values('06' , '03' , 34);insert into SC values('07' , '02' , 89);insert into SC values('07' , '03' , 98);

02 表结构预览

--学生表
Student(SId,Sname,Sage,Ssex)
--SId 学生编号,Sname 学生姓名,Sage 出生年月,Ssex 学生性别
--课程表
Course(CId,Cname,TId)
--CId 课程编号,Cname 课程名称,TId 教师编号
--教师表
Teacher(TId,Tname)
--TId 教师编号,Tname 教师姓名
--成绩表
SC(SId,CId,score)
--SId 学生编号,CId 课程编号,score 分数

1. 查询“01”课程比“02”课程成绩高的所有学生的学号；

select distinct t1.sid as sidfrom (select * from sc where cid='01')t1left join  (select * from sc where cid='02')t2on t1.sid=t2.sidwhere t1.score>t2.score

2. 查询平均成绩大于60分的同学的学号和平均成绩；

select sid    ,avg(score)from scgroup by sidhaving avg(score)>60

3. 查询所有同学的学号、姓名、选课数、总成绩

select student.sid as sid ,sname ,count(distinct cid) course_cnt ,sum(score) as total_scorefrom studentleft join scon student.sid=sc.sidgroup by sid,sname

4. 查询姓“李”的老师的个数；

select count(distinct tid) as teacher_cntfrom teacherwhere tname like '李%'

5. 查询没学过“张三”老师课的同学的学号、姓名；

select sid,snamefrom studentwhere sid not in  ( select sc.sid from teacher left join course on teacher.tid=course.tid left join sc on course.cid=sc.cid where teacher.tname='张三' )

6. 查询学过“01”并且也学过编号“02”课程的同学的学号、姓名；

select t.sid as sid ,snamefrom  ( select sid ,count(if(cid='01',score,null)) as count1 ,count(if(cid='02',score,null)) as count2 from sc group by sid having count(if(cid='01',score,null))>0 and count(if(cid='02',score,null))>0 )tleft join student on t.sid=student.sid

7. 查询学过“张三”老师所教的课的同学的学号、姓名；

select student.sid    ,snamefrom  ( select distinct cid from course left join teacher on course.tid=teacher.tid where teacher.tname='张三' )courseleft join sc  on course.cid=sc.cidleft join student on sc.sid=student.sidgroup by student.sid,sname

8. 查询课程编号“01”的成绩比课程编号“02”课程低的所有同学的学号、姓名；

select t1.sid,snamefrom  ( select distinct t1.sid as sid from (select * from sc where cid='01')t1 left join (select * from sc where cid='02')t2 on t1.sid=t2.sid where t1.score>t2.score )t1left join student on t1.sid=student.sid

9. 查询所有课程成绩小于60分的同学的学号、姓名；

select t1.sid,snamefrom  ( select sid,max(score) from sc group by sid having max(score<60) )t1left join student on t1.sid=student.sid

10. 查询没有学全所有课的同学的学号、姓名；

select t1.sid,snamefrom  ( select count(cid),sid from sc group by sid having count(cid) < (select count(distinct cid) from course) )t1left join student on t1.sid=student.sid

11. 查询至少有一门课与学号为“01”的同学所学相同的同学的学号和姓名；

select distinct sc.sidfrom  ( select cid from sc where sid='01' )t1left join sc on t1.cid=sc.cid

12. 查询和"01"号的同学学习的课程完全相同的其他同学的学号和姓名

#注意是和'01'号同学课程完全相同但非学习课程数相同的,这里我用左连接解决这个问题select t1.sid,snamefrom ( select sc.sid ,count(distinct sc.cid) from ( select cid from sc where sid='01' )t1 #选出01的同学所学的课程 left join sc on t1.cid=sc.cid group by sc.sid having count(distinct sc.cid)= (select count(distinct cid) from sc where sid = '01')    )t1left join student on t1.sid=student.sidwhere t1.sid!='01'

13. 把“SC”表中“张三”老师教的课的成绩都更改为此课程的平均成绩；

#暂跳过update题目

14. 查询没学过"张三"老师讲授的任一门课程的学生姓名

select     snamefrom studentwhere sid not in ( select distinct sid from sc left join course on sc.cid=course.cid left join teacher on course.tid=teacher.tid where tname='张三' )

15. 查询两门及其以上不及格课程的同学的学号，姓名及其平均成绩

select t1.sid,sname,avg_scorefrom  ( select sid,count(if(score<60,cid,null)),avg(score) as avg_score from sc group by sid having count(if(score<60,cid,null)) >=2 )t1left join student on t1.sid=student.sid

16. 检索"01"课程分数小于60，按分数降序排列的学生信息

select sid,if(cid='01',score,100)from scwhere if(cid='01',score,100)<60order by if(cid='01',score,100) desc

17. 按平均成绩从高到低显示所有学生的平均成绩

select sid,avg(score)from scgroup by sidorder by avg(score) desc

18. 查询各科成绩最高分、最低分和平均分：以如下形式显示：课程ID，课程name，最高分，最低分，平均分，及格率

select sc.cid ,cname ,max(score) as max_score ,min(score) as min_score ,avg(score) as avg_score ,count(if(score>=60,sid,null))/count(sid) as pass_rate from sc  left join course on sc.cid=course.cid group by sc.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

#这里先按照平均成绩排序，再按照及格百分数排序，select cid ,avg(score) as avg_score ,count(if(score>=60,sid,null))/count(sid) as pass_ratefrom scgroup by cidorder by avg_score,pass_rate desc

20. 查询学生的总成绩并进行排名

select sid ,sum(score) as sum_scorefrom scgroup by sidorder by sum_score desc

21. 查询不同老师所教不同课程平均分从高到低显示

select tid ,avg(score) as avg_scorefrom courseleft join sc on course.cid=sc.cidgroup by tidorder by avg_score desc

22. 查询所有课程的成绩第2名到第3名的学生信息及该课程成绩

select sid,rank_num,score,cidfrom ( select rank() over(partition by cid order by score desc) as rank_num ,sid ,score ,cid from sc )twhere rank_num in (2,3)

23. 统计各科成绩各分数段人数：课程编号,课程名称,[100-85],[85-70],[70-60],[0-60]及所占百分比

select sc.cid ,cname ,count(if(score between 85 and 100,sid,null))/count(sid) ,count(if(score between 70 and 85,sid,null))/count(sid) ,count(if(score between 60 and 70,sid,null))/count(sid) ,count(if(score between 0 and 60,sid,null))/count(sid)from scleft join course on sc.cid=course.cidgroup by sc.cid,cname

24. 查询学生平均成绩及其名次

select sid ,avg_score ,rank() over (order by avg_score desc)from  ( select sid ,avg(score) as avg_score from sc group by sid )t

25. 查询各科成绩前三名的记录

select sid,cid,rank1from ( select cid ,sid ,rank() over(partition by cid order by score desc) as rank1 from sc )twhere rank1<=3

26. 查询每门课程被选修的学生数

select count(sid) ,cidfrom scgroup 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 sidfrom scgroup by sidhaving count(cid) =1

28. 查询男生、女生人数

select ssex ,count(distinct sid)from studentgroup by ssex

29. 查询名字中含有"风"字的学生信息

select sid,snamefrom studentwhere sname like '%风%'

30. 查询同名同性学生名单，并统计同名人数

select ssex ,sname ,count(sid)from studentgroup by ssex,snamehaving count(sid)>=2

31. 查询1990年出生的学生名单(注：Student表中Sage列的类型是datetime)

select sid,sname,sagefrom studentwhere year(sage)=1990

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) as avg_scorefrom scgroup by cidorder by avg_score,cid desc

33. 查询不及格的课程，并按课程号从大到小排列

select cid,sid,scorefrom scwhere score<60order by cid desc,sid

34. 查询课程编号为"01"且课程成绩在60分以上的学生的学号和姓名；

select sid,cid,scorefrom scwhere cid='01' and score>60

35. 查询选修“张三”老师所授课程的学生中，成绩最高的学生姓名及其成绩

select sc.sid,sname,cname,scorefrom scleft join course style="font-weight: 600;">=course.cidleft join teacher style="font-weight: 600;">=teacher.tidleft join student style="font-weight: 600;">=student.sidwhere tname='张三'order by score desclimit 1;

36. 查询每门功课成绩最好的前两名

select    cid,sid,rank1from  ( select cid ,sid ,rank() over(partition by cid order by score desc) as rank1 from sc )twhere rank1 <=2

37. 统计每门课程的学生选修人数（超过5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，若人数相同，按课程号升序排列

select cid ,count(sid) as cntfrom scgroup by cidhaving cnt>=5order by count(sid) desc,cid

38. 检索至少选修两门课程的学生学号

select sid ,count(cid)from scgroup by sidhaving count(cid)>=2

39. 查询选修了全部课程的学生信息

select sid ,count(cid)from scgroup by sidhaving count(cid)=(select count(distinct cid) from sc)

40. 查询各学生的年龄

select sid,sname,year(curdate())-year(sage) as sagefrom student

41 查询本周过生日的学生

select sid,sname,sagefrom studentwhere weekofyear(sage)=weekofyear(curdate())

42. 查询下周过生日的学生

select sid,sname,sagefrom studentwhere weekofyear(sage) = weekofyear(date_add(curdate(),interval 1 week))

43 查询本月过生日的学生

select sid,sname,sagefrom studentwhere month(sage) = month(curdate())

44. 查询下月过生日的学生

select sid,sname,sagefrom studentwhere month(date_sub(sage,interval 1 month)) = month(curdate())End.作者：tomocat来源：知乎

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