SQL(基础例题+SQLserver实现)

例题：

/*
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
*/

/*例题相关数据*/
use dbtest--create table Student (SId varchar(10), Sname nvarchar(10), Sage datetime, Ssex varchar(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', '1990-12-20', '男');
insert into Student values('04', '李云', '1990-12-06', '男');
insert into Student values('05', '周梅', '1991-12-01', '女');
insert into Student values('06', '吴兰', '1992-01-01', '女');
insert into Student values('07', '郑竹', '1989-01-01', '女');
insert into Student values('09', '张三', '2017-12-20', '女');
insert into Student values('10', '李四', '2017-12-25', '女');
insert into Student values('11', '李四', '2012-06-06', '女');
insert into Student values('12', '赵六', '2013-06-13', '女');
insert into Student values('13', '孙七', '2014-06-01', '女');select *
from student--create table Course(CId varchar(10), Cname nvarchar(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');select *
from Course--create table Teacher(TId varchar(10), Tname nvarchar(10));
insert into Teacher values('01' , '张三');
insert into Teacher values('02' , '李四');
insert into Teacher values('03' , '王五');select *
from Teacher--create table SC(SId varchar(10), CId varchar(10), score decimal(6,1));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);

/*例题详解*/
--Q1:查询" 01 "课程比" 02 "课程成绩高的学生的信息及课程分数
select Student.*, t1.score, t2.score
from Student,(select SId, score from SC where SC.CId = '01') as t1,(select SId, score from SC where SC.CId = '02') as t2
where Student.SId = t1.SId  AND Student.SId = t2.SId AND t1.score > t2.scoreselect * from Student right join
(
select t1.SId, pro1, pro2 from(select SId, score as pro1 from SC where CId = '01') as t1,(select SId, score as pro2 from SC where CId = '02') as t2
where t1.SId = t2.SId AND t1.pro1 > t2.pro2
) as r
on Student.SId = r.SId;--Q1.1:查询同时存在" 01 "课程和" 02 "课程的情况
select *
from Student,(select SId, score from SC where CId = '01') as t1,(select SId, score from SC where CId = '02') as t2
where Student.SId = t1.SId AND Student.SId = t2.SIdselect * from Student
right join(
select t1.SId, pro1, pro2 from (select SId, score as pro1 from SC where CId = '01') as t1,(select SId, score as pro2 from SC where CId = '02') as t2where t1.SId = t2.SId) as r
on Student.SId = r.SId--Q1.2: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 Student,(select t1.SId, C1, S1, C2, S2 from(select SId, CId as C1, score as S1 from SC where CId = '01') as t1left join (select SId, CId as C2, score as S2 from SC where CId = '02') as t2 on t1.SId = t2.SId) as t3
where Student.SId = t3.SId--Q1.3:查询不存在" 01 "课程但存在" 02 "课程的情况
select * fromStudent,(select * from SC where SC.SId not in (select SId from SC where CId = '01')) as t1
where Student.SId = t1.SId--Q2: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, Student.Sname, pro
from Student
inner join (select SId, avg(score) as pro from SC group by SId having avg(score) >= 60) as t1
on Student.SId = t1.SId--Q3:查询在 SC 表存在成绩的学生信息
select Student.*
from Student
inner join (select SId from SC group by SId) as t1
on Student.SId = t1.SId--Q4: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 Student.SId, Student.Sname, C, S
from Student
left join (select SId, count(CId) as C, sum(score) as S from SC group by SId) as t1
on Student.SId = t1.SId--Q4.1:查有成绩的学生信息
select Student.SId, Student.Sname, C, S
from Student
inner join (select SId, count(CId) as C, sum(score) as S from SC group by SId) as t1
on Student.SId = t1.SId--Q5:查询「李」姓老师的数量
select count(TId) as num
from Teacher
where Teacher.Tname like '李%'--Q6:查询学过「张三」老师授课的同学的信息
select Student.*
from Studentinner join
(select SId from SC where CId = (select CId from Course where TId = (select TId from Teacher where Tname = '张三'))
) as t1
on Student.SId = t1.SId--Q7:查询没有学全所有课程的同学的信息
select Student.*
from Student
inner join
(select SId from SC
group by SId
having count(CId) < (select count(CId) as C from Course)
) as t1
on Student.SId = t1.SId--Q8: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 Student.*
from Student,
(select SId from(select SId, CId from SC where SId != '01') as t1,(select CId from SC where SId = '01') as t2
where t1.CId = t2.CId
group by SId
) as t3
where Student.SId = t3.SId--Q9: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 Student.*
from Student,(select SId from(select CId, count(CId) over() as C1 from SC where SId = '01') as t4,(select t1.*, C from(select SId, CId from SC) as t1,(select SId, count(CId) as C from SC where SId != '01' group by SId) as t2where t1.SId = t2.SId) as t3where t4.CId = t3.CId AND t4.C1 = t3.Cgroup by SId) as t5
where Student.SId = t5.SId--Q10:查询没学过"张三"老师讲授的任一门课程的学生姓名
select Student.Sname from Student
inner join
(select SId from SC where SId not in (select SId from SC where CId = (select CId from Course where TId = (select TId from Teacher where Tname = '张三')))
group by SId
) as t1
on Student.SId = t1.SId--Q11: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, pro
from Student,(select SId, count(score) as num, avg(score) as profrom SC where score < 60 group by SId) as t1
where Student.SId = t1.SId--Q12:检索" 01 "课程分数小于 60，按分数降序排列的学生信息
select Student.*
from Student
inner join(select SId, score from SC where CId = '01' AND score < 60) as t1
on Student.SId = t1.SId
order by score DESC--Q13: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 t1.*, pro
from
(select SId, score from SC) as t1,
(select SId, avg(score) as pro from SC group by SId
) as t2
where t1.SId = t2.SId
order by pro DESC--Q14: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 CId, count(*) as '选修人数', max(score) as '最高分', min(score) as '最低分',
convert(decimal(3,1), avg(score)) as '平均分',
(sum(case when SC.score >= 60 then 1 else 0 end) * 100 / count(*)) as '及格率%',
(sum(case when SC.score >= 70 AND SC.score < 80 then 1 else 0 end) * 100 / count(*)) as '中等率%',
(sum(case when SC.score >= 80 AND SC.score < 90 then 1 else 0 end) *100 / count(*)) as '优良率%',
(sum(case when SC.score >= 90 then 1 else 0 end) * 100 / count(*)) as '优秀率%'
from SC
group by CId/*
ROW_NUMBER()函数:相同数据，先查出的排名在前，没有重复值
RANK()函数:相同数据，排名相同，下一位直接跳过顺序值，并加上上一个重复的个数，如两个第一，下一个将是第三
DENSE_RANK()函数:相同数据，排名相同，下一位直接接着上一位的排名，如两个第一，下一个将是第二
*/
--Q15: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 a.SId, a.CId, a.score, count(b.score)+1 as pro
from SC as a
left join SC as b on a.CId = b.CId and b.score > a.score
group by a.CId, a.SId, a.score
order by CId, pro ASCselect *, RANK() over(partition by CId order by score DESC) as class
from SC--Q15.1:按各科成绩进行排序，并显示排名， Score 重复时合并名次
select *, DENSE_RANK() over(partition by CId order by score DESC) as class
from SC--Q16: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 *, DENSE_RANK() over(order by total DESC) as class
from(select SC.SId, sum(SC.score) as total from SCgroup by SC.SId
) as A--Q16.1: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 *, RANK() over(order by total DESC) as class
from(select SC.SId, sum(SC.score) as total from SCgroup by SC.SId
) as A--Q17: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 SC.CId, Course.Cname,sum(case when score > 85 AND score <= 100 then 1 else 0 end) as '[100-85]',cast(sum(case when score > 85 AND score <= 100 then 1 else 0 end) * 100 / count(*) as varchar(20)) + '%' as rate1,sum(case when score > 70 AND score <= 85 then 1 else 0 end) as '[85-70]',cast(sum(case when score > 70 AND score <= 85 then 1 else 0 end) * 100 / count(*) as varchar(20)) + '%' as rate2,sum(case when score > 60 AND score <= 70 then 1 else 0 end) as '[70-60]',cast(sum(case when score > 60 AND score <= 70 then 1 else 0 end) * 100 / count(*) as varchar(20)) + '%' as rate3,  sum(case when score <= 60 then 1 else 0 end) as '[60-0]',cast(sum(case when score <= 60 then 1 else 0 end) * 100 / count(*) as varchar(20)) + '%' as rate4
from SC
inner join Course on SC.CId = Course.CId
group by SC.CId, Course.Cname--Q18:查询各科成绩前三名的记录
select *
from (select *, ROW_NUMBER() over(partition by CId order by score DESC) as classfrom SC) as A
where class <= 3--Q19:查询每门课程被选修的学生数
select CId, count(CId) as num
from SC
group by CId--Q20:查询出只选修两门课程的学生学号和姓名
select SC.SId, Sname, count(CId) as num
from SC, Student
where SC.SId = Student.SId
group by SC.SId, Sname
having count(CId) = 2--Q21:查询男生、女生人数
select Ssex, count(Ssex) as num
from Student
group by Ssex--Q22:查询名字中含有「风」字的学生信息
select *
from Student
where Sname like '%风%'--Q23:查询同名同性学生名单，并统计同名人数
select Student.*, count(SId) over() as num
from Student
inner join (select Sname, Ssex, count(Sname) as num1, count(Ssex) as num2from Studentgroup by Sname, Ssexhaving count(Sname) > 1 AND count(Ssex) > 1
) as a
on Student.Sname = a.Sname--Q24:查询1990年出生的学生名单
select *
from Student
where YEAR(Student.Sage) = 1990--Q25: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 CId, avg(score) as pro
from SC
group by CId
order by pro DESC, CId ASC--Q26: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 a.SId, Sname, a.pro
from (select SC.SId, avg(score) as profrom SCgroup by SC.SIdhaving avg(score) >= 85) as a, Student
where a.SId = Student.SId--Q27:查询课程名称为「数学」，且分数低于 60 的学生姓名和分数
select Sname, score
from Student
inner join SC on Student.SId = SC.SId
where SC.CId = (select CId from Course where Cname = '数学') AND score < 60--Q28: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.SId, SC.CId, SC.score
from Student
left join SC on Student.SId =SC.SId--Q29: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 Sname, Cname, score
from (select *from SCwhere SId not in (select SId from SC where score < 70)) as a,Student,Course
where a.SId = Student.SId AND a.CId = Course.CId
order by Sname--Q30:查询不及格的课程
select DISTINCT CId
from SC
where score < 60--Q31: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
inner join SC on Student.SId = SC.SId
where SC.CId = 01 AND SC.score >= 80--Q32:求每门课程的学生人数
select CId, count(CId) as num
from SC
group by CId--Q33: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 TOP 1 Student.*, score, ROW_NUMBER() over(order by score DESC) as class
from Student
inner join SC on Student.SId = SC.SId
where SC.CId = (select CId from Course where TId = (select TId from Teacher where Tname = '张三'))--Q34: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 Student.*, score, RANK() over(order by score DESC) as classfrom Studentinner join SC on Student.SId = SC.SIdwhere SC.CId = (select CId from Course where TId = (select TId from Teacher where Tname = '张三'))) as a
where a.class = 1--Q35: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 as a
inner join SC as b on a.SId = b.SId
where a.CId != b.CId AND a.score = b.score--Q36:查询每门功课成绩最好的前两名
select *
from (select *, ROW_NUMBER() over(partition by CId order by score DESC) as classfrom SC) as a
where class < 3--Q37:统计每门课程的学生选修人数（超过 5 人的课程才统计）。
use dbtest
select CId, count(CId) as num
from SC
group by CId
having count(CId) > 5--Q38:检索至少选修两门课程的学生学号
select SId, count(SId) as num
from SC
group by SId
having count(SId) > 1--Q39:查询选修了全部课程的学生信息
select Student.*
from Student,(select SId from SCgroup by SIdhaving count(SId) = (select count(*) from Course)
) as a
where Student.SId = a.SId--Q40:查询各学生的年龄，只按年份来算
select Student.*, (select YEAR(GETDATE()) - YEAR(Student.Sage)) as '年龄'
from Student--Q41: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 Student.*,
(select YEAR(GETDATE()) - YEAR(Student.Sage) + (case when MONTH(GETDATE()) > MONTH(Student.Sage) OR (MONTH(GETDATE()) = MONTH(Student.Sage) AND DAY(GETDATE()) > DAY(Student.Sage)) then 0 else -1 end)) as '年龄'
from Student--Q42:查询本周过生日的学生
insert into Student(SId, Sname, Sage, Ssex)
values('14', '王五', '1997-09-01', '男')
insert into Student(SId, Sname, Sage, Ssex)
values('15', '钱峰', '1996-09-08', '男')
insert into Student(SId, Sname, Sage, Ssex)
values('16', '莫离', '1995-10-08', '男')delete from Student
where SId > 13select *
from Student
where DATEPART(wk, Student.Sage) = DATEPART(wk, GETDATE())--Q43:查询下周过生日的学生
select *
from Student
where DATEPART(wk, Student.Sage) = DATEPART(wk, GETDATE()) + 1 --Q44:查询本月过生日的学生
select *
from Student
where MONTH(Student.Sage) = MONTH(GETDATE())--Q45:查询下月过生日的学生
select *
from Student
where MONTH(Student.Sage) = MONTH(GETDATE()) + 1

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