建表
1.学生表
Student(Sno,Sname,Sage,Ssex)
Sno 学生编号,Sname 学生姓名,Sage 出生年月,Ssex 学生性别
2.课程表
Course(Cno,Cname,Tno)
Cno --课程编号,Cname 课程名称,T# 教师编号
3.教师表
Teacher(Tno,Tname)
Tno 教师编号,Tname 教师姓名
4.成绩表
SC(Sno,Cno,score)
Sno 学生编号,Cno 课程编号,score 分数
学生表 student
create table Student(Sno varchar(10),Sname varchar(10),Sage datetime,Ssex varchar(10))
insert into Student (Sno,Sname,Sage,Ssex) values(‘01’ , ‘赵雷’ , ‘1990-01-01’ , ‘男’);
insert into Student (Sno,Sname,Sage,Ssex) values(‘02’ , ‘钱电’ , ‘1990-12-21’ , ‘男’);
insert into Student (Sno,Sname,Sage,Ssex) values(‘03’ , ‘孙风’ , ‘1990-05-20’ , ‘男’);
insert into Student (Sno,Sname,Sage,Ssex) values(‘04’ , ‘李云’ , ‘1990-08-06’ , ‘男’);
insert into Student (Sno,Sname,Sage,Ssex) values(‘05’ , ‘周梅’ , ‘1991-12-01’ , ‘女’);
insert into Student (Sno,Sname,Sage,Ssex) values(‘06’ , ‘吴兰’ , ‘1992-03-01’ , ‘女’);
insert into Student (Sno,Sname,Sage,Ssex) values(‘07’ , ‘郑竹’ , ‘1989-07-01’ , ‘女’);
insert into Student (Sno,Sname,Sage,Ssex) values(‘08’ , ‘王菊’ , ‘1990-01-20’ , ‘女’);
科目表 Course
create table Course(Cno varchar(10),Cname varchar(10),Tno varchar(10))
insert into Course values(‘01’ , N’语文’ , ‘02’);
insert into Course values(‘02’ , N’数学’ , ‘01’);
insert into Course values(‘03’ , N’英语’ , ‘03’);
教师表 Teacher
create table Teacher(Tno 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’);
成绩表 SC
create table SC(Sno varchar(10),Cno 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);
练习题
５０道练习题
1 查询" 01 “课程比” 02 "课程成绩高的学生的信息及课程分数
1-1 查询同时存在" 01 “课程和” 02 "课程的情况
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 )
1-3. 查询不存在" 01 “课程但存在” 02 "课程的情况
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
3 查询在 SC 表存在成绩的学生信息
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 )
4-1 查有成绩的学生信息
5.查询「李」姓老师的数量
6.查询学过「张三」老师授课的同学的信息
7.查询没有学全所有课程的同学的信息
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息
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
10.查询没学过"张三"老师讲授的任一门课程的学生姓名
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
12 检索" 01 "课程分数小于 60，按分数降序排列的学生信息
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
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
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
15-1 按各科成绩进行排序，并显示排名， Score 重复时合并名次
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
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
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
18.查询各科成绩前三名的记录
19.查询每门课程被选修的学生数
20.查询出只选修两门课程的学生学号和姓名
21.查询男生、女生人数
22.查询名字中含有「风」字的学生信息
23.查询同名同性学生名单，并统计同名人数
24 查询 1990 年出生的学生名单
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
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
27.查询课程名称为「数学」，且分数低于 60 的学生姓名和分数
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）
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
30.查询不及格的课程
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
32.求每门课程的学生人数
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
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
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
36.查询每门功成绩最好的前两名
37.统计每门课程的学生选修人数（超过 5 人的课程才统计）。
38.检索至少选修两门课程的学生学号
39.查询选修了全部课程的学生信息
40.查询各学生的年龄，只按年份来算
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
42.查询本周过生日的学生
43.查询下周过生日的学生
44.查询本月过生日的学生
45.查询下月过生日的学生
个人答案（若有错误请赐教）
-- 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 c.*,d.cno,d.score
from student c left join sc d on c.sno=d.sno
where c.sno in (select a.sno
from
(select * from sc where cno='01')A left join
(select * from sc where cno='02')B on A.sno=B.sno
where a.score > b.score)
-- 1.1 查询同时存在" 01 "课程和" 02 "课程的情况
select a.sname,b.cno,b.score,c.cno,c.score
from student a
join(
select *
from sc
where cno = '01')b on a.sno=b.sno
join(
select *
from sc
where cno = '02')c on a.sno=c.sno
-- 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 a.sname,b.cno as cno1,b.score as score1,c.cno as cno2,c.score as score2
from student a
join(select *
from sc
where cno = '01')b on a.sno=b.sno
left join(
select *
from sc
where cno ='02')c on a.sno=c.sno
-- 1.3 查询不存在" 01 "课程但存在" 02 "课程的情况
select *
from(select a.sname,b.cno as cno1,b.score as score1,c.cno as cno2,c.score as score2
from student a
left join(select *
from sc
where cno = '01')b on a.sno=b.sno
join(
select *
from sc
where cno ='02')c on a.sno=c.sno)t
where t.score1 is null
-- 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 a.sno,b.sname,a.平均成绩
from
(select sno,avg(score) as '平均成绩'
from sc
group by sno
having avg(score)>=60)a left join student b
on a.sno=b.sno
-- 3. 查询在 SC 表存在成绩的学生信息
select distinct b.*
from sc a left join student b on a.sno = b.sno
-- 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 a.sno,a.sname,b.选课总数,b.总成绩
from ((select sno,sname from student)a
left join (select sno,count(cno) as '选课总数',sum(score) as '总成绩' from sc group by sno)b on a.sno=b.sno)
-- 4.1 查有成绩的学生信息
select *
from student
where sno in (select distinct sno from sc)
-- 5. 查询「李」姓老师的数量
select count(tno)
from teacher
where tname like '李%'
-- 6. 查询学过「张三」老师授课的同学的信息
select *
from student
where sno in
(select sno
from sc
where cno in
(select cno
from teacher a left join course b on a.tno=b.tno
where tname = '张三'))
-- 7. 查询没有学全所有课程的同学的信息
select *
from student
where sno in
(select sno
from sc
group by Sno
having count(cno) !=
(select count(cno)
from course) and count(cno) !=0 )
-- 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息
select *
from student
where sno in (select distinct sno
from sc
where cno in (select cno
from sc
where sno = '01') and sno !='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 B.* from (select * from student where Sno!='01') B JOIN (select Sno,GROUP_CONCAT(Cno) gc from sc GROUP BY Sno ) A on A.Sno=B.Sno where A.gc=(select GROUP_CONCAT(Cno) from sc where Sno='01')
select *
from student
where sno in (
select sno
from (select sno,group_concat(cno) gc from sc where sno != '01' group by sno)t
where t.gc=(select GROUP_CONCAT(Cno) from sc where Sno='01'))
-- 10. 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 sno not in
(select sno
from sc
where cno = (select b.cno
from teacher a left join course b on a.tno=b.tno
where a.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 a.sno,b.sname,avg(a.score)
from sc a left join student b on a.sno=b.sno
where a.sno in (select t.sno
from(select *
from sc
where score<60)t
group by t.sno
having count(t.sno) >=2)
group by a.sno,b.sname
-- 12. 检索" 01 "课程分数小于 60，按分数降序排列的学生信息
select b.*,a.score
from sc a left join student b on a.sno=b.sno
where cno='01' and score < 60
order by 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 a.*,b.平均成绩
from sc a left join (select sno,avg(score) as '平均成绩'
from sc
group by sno)b on a.sno = b.sno
order by b.平均成绩 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 distinct a.cno,b.cname,c.最高分,c.最低分,c.平均分,d.及格率,e.中等率,f.优良率,g.优秀率
from sc a
left join course b on a.cno = b.cno
left join (select cno,max(score) as '最高分',min(score) as '最低分',avg(score) as '平均分' from sc group by cno )c on a.cno=c.cno
left join (select cno,sum(case when score>=60 then 1 else 0 end)/count(*) as '及格率' from sc group by cno)d on a.cno=d.cno
left join (select cno,sum(case when score >= 70 and score< 80 then 1 else 0 end)/count(*) as '中等率' from sc group by cno)e on a.cno = e.cno
left join (select cno,sum(case when score >= 80 and score< 90 then 1 else 0 end)/count(*) as '优良率' from sc group by cno)f on a.cno=f.cno
left join (select cno,sum(case when score >=90 then 1 else 0 end)/count(*) as '优秀率' from sc group by cno)g on a.cno = g.cno
SELECT a.cno, b.cname, MAX(a.score) 最高分, MIN(a.score)最低分, AVG(a.score) 平均分,
COUNT(IF(a.score>=60, sno, NULL)) / COUNT(sno) 及格率,
COUNT(IF(a.score>=70 and a.score <80, sno, NULL)) / COUNT(sno) 中等率,
COUNT(IF(a.score>=80 and a.score <90, sno, NULL)) / COUNT(sno)良好率,
COUNT(IF(a.score>=90, sno, NULL)) / COUNT(sno) 优秀率
FROM sc a
LEFT JOIN course b ON b.cno = a.cno
GROUP BY cno,Cname
-- 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 *,RANK()over(partition by cno order by score desc)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 cno,sno,score,dense_rank() over (partition by cno order by score desc) as `rank`
from sc
-- 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 t.*,rank()over(order by t.总成绩 desc) as '排名'
from(select sno,sum(score) as '总成绩'
from sc
group by sno)t
-- 16.1 查询学生的总成绩，并进行行排名，总分重复时不保留名次空缺
select t.*,dense_rank()over(order by t.总成绩 desc) as '排名'
from(select sno,sum(score) as '总成绩'
from sc
group by sno)t
-- 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 distinct a.cno,b.cname,c.`[100-85]`,c.所占百分比,d.`[85-70]`,d.所占百分比,e.`[70-60]`,e.所占百分比,f.`[60-0]`,f.所占百分比
from sc a
left join course b on a.cno=b.cno
left join (select cno,sum(case when score >85 and score<=100 then 1 else 0 end) as '[100-85]'
,(sum(case when score >85 and score<=100 then 1 else 0 end)/count(*))*100 as '所占百分比' from sc group by cno)c on a.cno=c.cno
left join (select cno,sum(case when score >70 and score<=85 then 1 else 0 end) as '[85-70]'
,(sum(case when score >70 and score<=85 then 1 else 0 end)/count(*))*100 as '所占百分比' from sc group by cno)d on a.cno=d.cno
left join (select cno,sum(case when score >60 and score<=70 then 1 else 0 end) as '[70-60]'
,(sum(case when score >60 and score<=70 then 1 else 0 end)/count(*))*100 as '所占百分比' from sc group by cno)e on a.cno=e.cno
left join (select cno,sum(case when score >=0 and score<=60 then 1 else 0 end) as '[60-0]'
,(sum(case when score >=0 and score<=60 then 1 else 0 end)/count(*))*100 as '所占百分比' from sc group by cno)f on a.cno=f.cno
-- 18. 查询各科成绩前三名的记录
select t.cno,t.sno,t.score,t.排名 from(select *,rank() over(partition by cno order by score desc) as '排名'
from sc)t where t.排名<4
SELECT a.cno,a.score,COUNT(B.score) +1 as ranking
FROM SC a LEFT JOIN SC b
ON a.Cno = b.Cno AND a.score<b.score
GROUP BY a.Cno,a.Sno,a.score
HAVING ranking <= 3
ORDER BY a.cno,ranking
-- 19. 查询每门课程被选修的学生数
select cno,count(*)
from sc
group by cno
-- 20. 查询出只选修两门课程的学生学号和姓名
select sno,sname
from student
where sno in
(select sno
from sc
group by sno
having count(sno) = 2)
-- 21. 查询男生、女生人数
select ssex,count(ssex) as '人数'
from student
group by ssex
-- 22. 查询名字中含有「风」字的学生信息
select *
from student
where sname like '%风%'
-- 23. 查询同名同性学生名单，并统计同名人数
select A.*,B.同名人数 from Student A
left join (select Sname,Ssex,COUNT(*)同名人数 from Student group by Sname,Ssex)B
on A.Sname=B.Sname and A.Ssex=B.Ssex
where B.同名人数>1
-- 24. 查询 1990 年出生的学生名单
select *
from student
having year(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 cno,avg(score)
from sc
group by cno
order by avg(score) desc,cno
-- 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 b.sno,a.sname,b.平均成绩
from student a join (select sno,avg(score) as '平均成绩'
from sc
group by sno
having avg(score)>=85)B
on a.sno=b.sno
-- 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 b.sname,a.score
from (select sno,score
from sc a left join course b on a.cno=b.cno
where cname = '数学' and score<60)a left join student b on a.sno=b.sno
-- 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 t.sno,t.sname,t.cno,d.cname,t.score
from (select a.sno,a.sname,b.cno,b.score
from student a left join sc b on a.sno=b.sno)t left join course d on t.cno = d.cno
-- 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 a.sname,b.cname,t.score
from(select *
from sc
where score >70)t left join student a on t.sno=a.sno
left join course b on t.cno=b.cno
-- 30. 查询不及格的课程
select a.sno,b.cname,a.score
from (select *
from sc
where score<60)a left join course b on a.cno=b.cno
-- 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 a.sno,b.sname
from (select sno from sc where cno='01' and score >80)a left join student b on a.sno=b.sno
-- 32. 求每门课程的学生人数
select cno,count(*)
from sc
group by cno
-- 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 * from (select sno,score,dense_rank() over(partition by cno order by score desc) as 'rank'
from sc
where cno in
(select a.cno
from course a left join teacher b on a.tno=b.tno
where b.tname = '张三'))t
where t.rank = 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 * from (select sno,score,dense_rank() over(partition by cno order by score desc) as 'rank'
from sc
where cno in
(select a.cno
from course a left join teacher b on a.tno=b.tno
where b.tname = '张三'))t
where t.rank = 1
-- 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 distinct a.*
from sc a join sc b on a.Sno=b.Sno
where a.score=b.score and a.Cno!=b.Cno
-- 36. 查询每门课成绩最好的前两名
select t.*
from(select *,row_number() over(partition by cno order by score desc) as 'rank'
from sc)t
where t.`rank` <= 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）。
select cno,count(*)
from sc
group by cno
having count(*) >5
-- 38. 检索至少选修两门课程的学生学号
select sno,count(*)
from sc
group by sno
having count(*)>=2
-- 39. 查询选修了全部课程的学生信息
select *
from student
where sno in (select sno from sc group by sno having count(*) = (select count(distinct cno) from sc ))
-- 40. 查询各学生的年龄，只按年份来算
select sno,sname,(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 sage,(DATE_FORMAT(NOW(),'%Y')-DATE_FORMAT(sage,'%Y') -
(case when DATE_FORMAT(NOW(),'%m%d')>DATE_FORMAT(sage,'%m%d') then 0 else 1 end)) as age
from student
-- 42. 查询本周过生日的学生
select *
from student
where WEEK(DATE_FORMAT(NOW(),'%Y%m%d'))=WEEK(sage)
select *
from student
where YEARWEEK(sage)=YEARWEEK(DATE_FORMAT(NOW(),'%Y%m%d'))
select WEEK(DATE_FORMAT(NOW(),'%Y%m%d')) #查看当前周数
-- 43. 查询下周过生日的学生
select *
from student
where WEEK(DATE_FORMAT(NOW(),'%Y%m%d'))=WEEK(sage)-1
-- 44. 查询本月过生日的学生
select *
from student
where month(DATE_FORMAT(NOW(),'%Y%m%d'))=month(sage)
-- 45. 查询下月过生日的学生
select *
from student
where month(DATE_FORMAT(NOW(),'%Y%m%d'))=month(sage)-1
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