练习前的准备

SQL环境搭建

https://www.jianshu.com/p/edca5142391c

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);

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

题目

1、查询“01”课程比“02”课程成绩高的所有学生的学号；
2、查询平均成绩大于60分的同学的学号和平均成绩；
3、查询所有同学的学号、姓名、选课数、总成绩
4、查询姓“李”的老师的个数；
5、查询没学过“张三”老师课的同学的学号、姓名；
6、查询学过编号“01”并且也学过编号“02”课程的同学的学号、姓名；
7、查询学过“张三”老师所教的课的同学的学号、姓名；
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；
9、查询所有课程成绩小于60分的同学的学号、姓名；
10、查询没有学全所有课的同学的学号、姓名；
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；
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
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；
14、查询没学过”张三”老师讲授的任一门课程的学生姓名
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
16、检索”01″课程分数小于60，按分数降序排列的学生信息
17、按平均成绩从高到低显示所有学生的平均成绩
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
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
20、查询学生的总成绩并进行排名
21、查询不同老师所教不同课程平均分从高到低显示
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
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
24、查询学生平均成绩及其名次
25、查询各科成绩前三名的记录
26、查询每门课程被选修的学生数
27、查询出只选修了一门课程的全部学生的学号和姓名
28、查询男生、女生人数
29、查询名字中含有”风”字的学生信息
30、查询同名同性学生名单，并统计同名人数
31、查询1990年出生的学生名单(注：Student表中Sage列的类型是datetime)
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
37、查询不及格的课程，并按课程号从大到小排列
38、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；
40、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
42、查询每门功课成绩最好的前两名
43、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
44、检索至少选修两门课程的学生学号
45、查询选修了全部课程的学生信息
46、查询各学生的年龄
47、查询本周过生日的学生
48、查询下周过生日的学生
49、查询本月过生日的学生
50、查询下月过生日的学生

答案

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 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

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 sc
group by sid
having 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_score
from student
left join sc 
on student.sid=sc.sid
group by sid,sname

4、查询姓“李”的老师的个数；

select
    count(distinct tid) as teacher_cnt
from teacher
where tname like '李%'

5、查询没学过“张三”老师课的同学的学号、姓名；

select
    sid,sname
from student
where 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
    ,sname
from 
    (
        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
    )t
left 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
    ,sname
from 
    (
        select
            distinct cid 
        from course
        left join teacher 
        on course.tid=teacher.tid
        where teacher.tname='张三'
    )course
left join sc 
    on course.cid=sc.cid
left join student
    on sc.sid=student.sid
group 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,sname
from 
    (
        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
    )t1
left 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,sname
from 
    (
        select
            sid,max(score)
        from sc
        group by sid
        having max(score<60)
    )t1
left 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,sname
from 
    (
        select
            count(cid),sid
        from sc
        group by sid
        having count(cid) < (select count(distinct cid) from course)
    )t1
left 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.sid
from 
    (
        select
            cid
        from sc
        where sid='01'
    )t1
left 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,sname
from
    (
        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')
    )t1
left join student
    on t1.sid=student.sid
where 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 
    sname
from student
where 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_score
from 
    (
        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
    )t1
left 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 sc
where if(cid='01',score,100)<60
order 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 sc
group by sid
order 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，题目有点奇怪
select 
    cid
    ,avg(score) as avg_score
    ,count(if(score>=60,sid,null))/count(sid) as pass_rate
from sc
group by cid
order 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_score
from sc
group by sid
order 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_score
from course
left join sc
    on course.cid=sc.cid
group by tid
order 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,cid
from
    (
        select
            rank() over(partition by cid order by score desc) as rank_num
            ,sid
            ,score
            ,cid
        from sc
    )t
where 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 sc
left join course
    on sc.cid=course.cid
group 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,rank1
from 
    (
        select
            cid
            ,sid
            ,rank() over(partition by cid order by score desc) as rank1
        from sc
    )t
where rank1<=3

26、查询每门课程被选修的学生数

select
    count(sid)
    ,cid
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

#只查出来sid即可，后面懒得交student表
select
    sid
from sc
group by sid
having count(cid) =1

28、查询男生、女生人数

select
    ssex
    ,count(distinct sid)
from student
group by ssex

29、查询名字中含有”风”字的学生信息

select
    sid,sname
from student
where sname like '%风%'

30、查询同名同性学生名单，并统计同名人数

#题目有歧义，这套题的质量感觉有点差
select
    ssex
    ,sname
    ,count(sid)
from student
group by ssex,sname
having 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,sage
from student
where 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_score
from sc
group by cid
order by avg_score,cid desc

37、查询不及格的课程，并按课程号从大到小排列

#有问题的题目
select
    cid,sid,score
from sc
where score<60
order by cid desc,sid

38、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,score
from sc
where cid='01' and score>60

40、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,score
from sc
left join course
    on sc.cid=course.cid
left join teacher
    on course.tid=teacher.tid
left join student
    on sc.sid=student.sid
where tname='张三'
order by score desc
limit 1;

42、查询每门功课成绩最好的前两名

##感觉题目重复了
select
    cid,sid,rank1
from 
    (
        select
            cid
            ,sid
            ,rank() over(partition by cid order by score desc) as rank1
        from sc 
    )t
where rank1 <=2

43、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 cnt
from sc
group by cid
having cnt>=5
order by count(sid) desc,cid

44、检索至少选修两门课程的学生学号

select
    sid
    ,count(cid)
from sc
group by sid
having count(cid)>=2

45、查询选修了全部课程的学生信息

#不太严谨，但实务中应该没问题，如需严谨见12题思路
select
    sid
    ,count(cid)
from sc
group by sid
having count(cid)=(select count(distinct cid) from sc)

46、查询各学生的年龄

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

47、查询本周过生日的学生

select
    sid,sname,sage
from student
where weekofyear(sage)=weekofyear(curdate())

48、查询下周过生日的学生

select 
    sid,sname,sage
from student
where weekofyear(sage) = weekofyear(date_add(curdate(),interval 1 week))

49、查询本月过生日的学生

select
    sid,sname,sage
from student
where month(sage) = month(curdate())

50、查询下月过生日的学生

select
    sid,sname,sage
from student
where month(date_sub(sage,interval 1 month)) = month(curdate())