MySQL45道练习题

作业需要数据表SQL语句已给

?1. 查询" 01 "课程比" 02 "课程成绩高的学生的信息及课程分数

select * from Student RIGHT JOIN (
    select t1.SId, class1, class2 from
          (select SId, score as class1 from sc where sc.CId = '01')as t1, 
          (select SId, score as class2 from sc where sc.CId = '02')as t2
    where t1.SId = t2.SId AND t1.class1 > t2.class2
)r on Student.SId = r.SId;

?1.1 查询同时存在" 01 "课程和" 02 "课程的情况

select * from 
    (select * from sc where sc.CId = '01') as t1, 
    (select * from sc where sc.CId = '02') as t2
where t1.SId = t2.SId;

1.2 查询存在" 01 "课程但可能不存在" 02 "课程的情况(不存在时显示为 null )

select * from 
(select * from sc where sc.CId = '01') as t1
left join 
(select * from sc where sc.CId = '02') as t2
on t1.SId = t2.SId;

1.3 查询不存在" 01 "课程但存在" 02 "课程的情况

select * from sc
where sc.SId not in (
    select SId from sc 
    where sc.CId = '01'
) and sc.CId= '02';

2.查询平均成绩大于等于 60 分的同学的学生编号和学生姓名和平均成绩

select student.SId,sname,ss from student,(
    select SId, AVG(score) as ss from sc  
    group by SId 
    having AVG(score)> 60
    )r where student.sid = r.sid;

3.查询在 SC 表存在成绩的学生信息

select distinct student.*
from student,sc
where student.SId=sc.SId

4.查询所有同学的学生编号、学生姓名、选课总数、所有课程的总成绩(没成绩的显示为 null )

select s.sid, s.sname,r.coursenumber,r.scoresum
from (
    (select student.sid,student.sname from student)s 
    left join 
    (select sc.sid, sum(sc.score) as scoresum, count(sc.cid) as coursenumber from sc group by sc.sid)r 
    on s.sid = r.sid);

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4.1 查有成绩的学生信息

select * from student where exists (select sc.sid from sc where student.sid = sc.sid);

5.查询「李」姓老师的数量

select count(*) from teacher where tname like '李%';

6.查询学过「张三」老师授课的同学的信息

select student.* from student,teacher,course,sc
where 
    student.sid = sc.sid 
    and course.cid=sc.cid 
    and course.tid = teacher.tid 
    and tname = '张三';

7.查询没有学全所有课程的同学的信息

select * from student
where student.sid not in (
  select sc.sid from sc
  group by sc.sid
  having count(sc.cid)= (select count(cid) from course));

8.查询至少有一门课与学号为" 01 "的同学所学相同的同学的信

select * from student 
where student.sid in (
    select sc.sid from sc 
    where sc.cid in(
        select sc.cid from sc 
        where sc.sid = '01'));

9.查询和" 01 "号的同学学习的课程 完全相同的其他同学的信息

select * from student where sid in(
select a.sid from (select sid,group_concat(cid order by cid) as courses 
from sc group by sid) as a
inner join (select sid,group_concat(cid order by cid) as courses 
from sc group by sid having sid='01') as b
on a.sid != 1 and a.courses = b.courses);

10.查询没学过"张三"老师讲授的任一门课程的学生姓名

select * from student
where student.sid not in(
    select sc.sid from sc,course,teacher 
    where
        sc.cid = course.cid
        and course.tid = teacher.tid
        and teacher.tname= "张三");

11.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 student.sid, student.Sname,b.avg
from student right join
(select sid, AVG(score) as avg from sc
    where sid in (
              select sid from sc 
              where score<60 
              group by sid 
              having count(score)>1)
    group by sid) b on student.sid=b.sid;

12.检索" 01 "课程分数小于 60，按分数降序排列的学生信息

select student.*, sc.score from student, sc
where student.sid = sc.sid
and sc.score < 60
and cid = "01"
order by sc.score desc;

13.按平均成绩从高到低显示所有学生的所有课程的成绩以及平均成绩

select *  from sc 
left join (
    select sid,avg(score) as avscore from sc 
    group by sid
    )r 
on sc.sid = r.sid
order by avscore desc;

14.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，中等率，优良率，优秀率;及格为>=60，中等为：70-80，优良为：80-90，优秀为：>=90;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 
sc.CId ,
max(sc.score)as 最高分,
min(sc.score)as 最低分,
AVG(sc.score)as 平均分,
count(*)as 选修人数,
sum(case when sc.score>=60 then 1 else 0 end )/count(*)as 及格率,
sum(case when sc.score>=70 and sc.score<80 then 1 else 0 end )/count(*)as 中等率,
sum(case when sc.score>=80 and sc.score<90 then 1 else 0 end )/count(*)as 优良率,
sum(case when sc.score>=90 then 1 else 0 end )/count(*)as 优秀率 
from sc
GROUP BY sc.CId
ORDER BY count(*)DESC, sc.CId ASC

15.按各科成绩进行排序，并显示排名， Score 重复时保留名次空缺

SELECT *,row_number() over (PARTITION BY cid ORDER BY score DESC) AS '排名'FROM sc;

15.1 按各科成绩进行排序，并显示排名， Score 重复时合并名次

select *,
case when @sco=score then @rank else @rank:=@rank+1 end as rn,
@sco:=score
from sc,(select @rank:=0,@sco:=NULL) t
order by score desc;

16.查询学生的总成绩，并进行排名，总分重复时保留名次空缺

select a.*,
@rank:=if(@sco=scos,'',@rank+1) as rn,
@sco:=scos
from
(select sid,sum(score) as scos from sc
group by sid order by scos desc) a,
(select @rank:=0,@sco:=NULL) b;

16.1 查询学生的总成绩，并进行排名，总分重复时不保留名次空缺

select a.*,
@rank:=if(@sco=scos,@rank,@rank+1) as rn,
@sco:=scos
from
(select sid,sum(score) as scos from sc
group by sid order by scos desc) a,
(select @rank:=0,@sco:=NULL) b;

17.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]，[60-0] 及所占百分比

select course.cname, course.cid,
sum(case when sc.score<=100 and sc.score>85 then 1 else 0 end) as "[100-85]",
sum(case when sc.score<=85 and sc.score>70 then 1 else 0 end) as "[85-70]",
sum(case when sc.score<=70 and sc.score>60 then 1 else 0 end) as "[70-60]",
sum(case when sc.score<=60 and sc.score>0 then 1 else 0 end) as "[60-0]"
from sc left join course on sc.cid = course.cid group by sc.cid;

18.查询各科成绩前三名的记录

select * from sc
where (
select count(*) from sc as a 
where sc.cid = a.cid and sc.score<a.score 
)< 3 order by cid asc, sc.score desc;

19.查询每门课程被选修的学生数

select cid, count(sid) from sc  group by cid;

20.查询出只选修两门课程的学生学号和姓名

select student.SId,student.Sname
from sc,student
where student.SId=sc.SId  
group by sc.SId
having count(*)=2；

21.查询男生、女生人数

select ssex, count(*) from student group by ssex;

22.查询名字中含有「风」字的学生信息

select * from student  where student.Sname like '%风%';

23.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;

24.查询 1990 年出生的学生名单

select * from student where YEAR(student.Sage)=1990;

25.查询每门课程的平均成绩，结果按平均成绩降序排列，平均成绩相同时，按课程编号升序排列

select sc.cid, course.cname, AVG(SC.SCORE) as average from sc, course
where sc.cid = course.cid group by sc.cid order by average desc,cid asc;

26.查询平均成绩大于等于 85 的所有学生的学号、姓名和平均成绩

select student.sid, student.sname, AVG(sc.score) as aver from student, sc
where student.sid = sc.sid group by sc.sid having aver > 85;

27.查询课程名称为「数学」，且分数低于 60 的学生姓名和分数

select student.sname, sc.score from student, sc, course
where student.sid = sc.sid and course.cid = sc.cid and course.cname = "数学" and sc.score < 60;

28.查询所有学生的课程及分数情况（存在学生没成绩，没选课的情况）

select student.sname, cid, score from student left join sc on student.sid = sc.sid;

29.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 student.sname, course.cname,sc.score from student,course,sc
where sc.score>70 and student.sid = sc.sid and sc.cid = course.cid;

30.查询不及格的课程

select distinct sc.CId from sc where sc.score <60;

31.查询课程编号为 01 且课程成绩在 80 分以上的学生的学号和姓名

select student.sid,student.sname from student,sc
where cid="01" and score>=80 and student.sid = sc.sid;

32.求每门课程的学生人数

select sc.cid,count(*) as 学生人数 from sc group by sc.cid;

33.成绩不重复，查询选修「张三」老师所授课程的学生中，成绩最高的学生信息及其成绩

select student.*, sc.score, sc.cid from student, teacher, course,sc 
where teacher.tid = course.tid
and sc.sid = student.sid
and sc.cid = course.cid
and teacher.tname = "张三"
order by score desc
limit 1;

34.成绩有重复的情况下，查询选修「张三」老师所授课程的学生中，成绩最高的学生信息及其成绩

select student.*, sc.score, sc.cid from student, teacher, course,sc 
where teacher.tid = course.tid
and sc.sid = student.sid
and sc.cid = course.cid
and teacher.tname = "张三"
and sc.score = (
    select Max(sc.score) 
    from sc,student, teacher, course
    where teacher.tid = course.tid
    and sc.sid = student.sid
    and sc.cid = course.cid
    and teacher.tname = "张三"
);

35.查询不同课程成绩相同的学生的学生编号、课程编号、学生成绩

select  a.cid, a.sid,  a.score from sc as a
inner join 
sc as b
on a.sid = b.sid
and a.cid != b.cid
and a.score = b.score
group by cid, sid;

36.查询每门功成绩最好的前两名

select a.sid,a.cid,a.score from sc as a left join sc as b 
on a.cid = b.cid and a.score<b.score
group by a.cid, a.sid having count(b.cid)<2 order by a.cid;

37.统计每门课程的学生选修人数（超过 5 人的课程才统计）。

select sc.cid, count(sid) as cc from sc group by cid having cc >5;

38.检索至少选修两门课程的学生学号

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

39.查询选修了全部课程的学生信息

select student.* from sc ,student where sc.SId=student.SId group by sc.SId having count(*) = (select distinct count(*) from course )

40.查询各学生的年龄，只按年份来算

select *, (year(now()) - year(sage)) as age from student;

41.按照出生日期来算，当前月日 < 出生年月的月日则，年龄减一

select *, timestampdiff(YEAR,sage,NOW()) as age from student;

42.查询本周过生日的学生

select * from student where WEEKOFYEAR(student.Sage)=WEEKOFYEAR(CURDATE());

43.查询下周过生日的学生

select * from student where WEEKOFYEAR(student.Sage)=WEEKOFYEAR(CURDATE())+1;

44.查询本月过生日的学生

select * from student where MONTH(student.Sage)=MONTH(CURDATE());

45.查询下月过生日的学生

select * from student where MONTH(student.Sage)=MONTH(CURDATE())+1;

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