50 个高级 sql 语句



 





问题及描述:



--1.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



--2.课程表



Course(CID,Cname,TID) --CID --课程编号,Cname 课程名称,TID 教师编号



--3.教师表



Teacher(TID,Tname) --TID 教师编号,Tname 教师姓名



--4.成绩表



SC(SID,CID,score) --SID 学生编号,CID 课程编号,score 分数



*/



--创建测试数据



create table Student(SID varchar(10),Sname nvarchar(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 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');



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');



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);



--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



select a.* , b.score 课程01的分数,c.score 课程02的分数 from Student a , SC b , SC c



where a.SID = b.SID and a.SID = c.SID and b.CID = '01' and c.CID = '02' and b.score > c.score



--1.2、查询同时存在"01"课程和"02"课程的情况和存在"01"课程但可能不存在"02"课程的情况(不存在时显示为null)(以下存在相同内容时不再解释)



select a.* , b.score 课程01的分数,c.score 课程02的分数 from Student a



left join SC b on a.SID = b.SID and b.CID = '01'



left join SC c on a.SID = c.SID and c.CID = '02'



where b.score > isnull(c.score,0)



方法1.1 sql 解析(基于 mysql 数据库,方法 1.2 不是mysql 数据库,mysql 数据库里面没有 isnull 函数)查询流程如下:





 




--2、查询"01"课程比"02"课程成绩低的学生的信息及课程分数



--2.1、查询同时存在"01"课程和"02"课程的情况



select a.* , b.score 课程01的分数 ,c.score 课程02的分数 from Student a , SC b , SC c



where a.SID = b.SID and a.SID = c.SID and b.CID = '01' and c.CID = '02' and b.score < c.score



--2.2、查询同时存在"01"课程和"02"课程的情况和不存在"01"课程但存在"02"课程的情况



select a.* , b.score 课程01的分数 ,c.score 课程02的分数 from Student a



left join SC b on a.SID = b.SID and b.CID = '01'



left join SC c on a.SID = c.SID and c.CID = '02'



where isnull(b.score,0) < c.score



--3、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.SID , a.Sname , cast(avg(b.score) as decimal(18,2)) avg_score



from Student a , sc b



where a.SID = b.SID



group by a.SID , a.Sname



having cast(avg(b.score) as decimal(18,2)) >= 60



order by a.SID



--4、查询平均成绩小于60分的同学的学生编号和学生姓名和平均成绩



--4.1、查询在sc表存在成绩的学生信息的SQL语句。



select a.SID , a.Sname , cast(avg(b.score) as decimal(18,2)) avg_score



from Student a , sc b



where a.SID = b.SID



group by a.SID , a.Sname



having cast(avg(b.score) as decimal(18,2)) < 60



order by a.SID



--4.2、查询在sc表中不存在成绩的学生信息的SQL语句。



select a.SID , a.Sname , isnull(cast(avg(b.score) as decimal(18,2)),0) avg_score



from Student a left join sc b



on a.SID = b.SID



group by a.SID , a.Sname



having isnull(cast(avg(b.score) as decimal(18,2)),0) < 60



order by a.SID



--5、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



--5.1、查询所有有成绩的SQL。



select a.SID 学生编号 , a.Sname 学生姓名 , count(b.CID) 选课总数, sum(score) 所有课程的总成绩



from Student a , SC b



where a.SID = b.SID



group by a.SID,a.Sname



order by a.SID



--5.2、查询所有(包括有成绩和无成绩)的SQL。



select a.SID 学生编号 , a.Sname 学生姓名 , count(b.CID) 选课总数, sum(score) 所有课程的总成绩



from Student a left join SC b



on a.SID = b.SID



group by a.SID,a.Sname



order by a.SID



--6、查询"李"姓老师的数量



--方法1



select count(Tname) 李姓老师的数量 from Teacher where Tname like '李%'



--方法2



select count(Tname) 李姓老师的数量 from Teacher where left(Tname,1) = '李'



--7、查询学过"张三"老师授课的同学的信息



select distinct Student.* from Student , SC , Course , Teacher



where Student.SID = SC.SID and SC.CID = Course.CID and Course.TID = Teacher.TID and Teacher.Tname = '张三'



order by Student.SID



--8、查询没学过"张三"老师授课的同学的信息



select m.* from Student m where SID not in (select distinct SC.SID from SC , Course , Teacher where SC.CID = Course.CID and Course.TID = Teacher.TID and Teacher.Tname = '张三') order by m.SID



--9、查询学过编号为"01"并且也学过编号为"02"的课程的同学的信息



--方法1



select Student.* from Student , SC where Student.SID = SC.SID and SC.CID = '01' and exists (Select 1 from SC SC_2 where SC_2.SID = SC.SID and SC_2.CID = '02') order by Student.SID



--方法2



select Student.* from Student , SC where Student.SID = SC.SID and SC.CID = '02' and exists (Select 1 from SC SC_2 where SC_2.SID = SC.SID and SC_2.CID = '01') order by Student.SID



--方法3



select m.* from Student m where SID in



(



select SID from



(



select distinct SID from SC where CID = '01'



union all



select distinct SID from SC where CID = '02'



) t group by SID having count(1) = 2



)



order by m.SID



--10、查询学过编号为"01"但是没有学过编号为"02"的课程的同学的信息



--方法1



select Student.* from Student , SC where Student.SID = SC.SID and SC.CID = '01' and not exists (Select 1 from SC SC_2 where SC_2.SID = SC.SID and SC_2.CID = '02') order by Student.SID



--方法2



select Student.* from Student , SC where Student.SID = SC.SID and SC.CID = '01' and Student.SID not in (Select SC_2.SID from SC SC_2 where SC_2.SID = SC.SID and SC_2.CID = '02') order by Student.SID



--11、查询没有学全所有课程的同学的信息



--11.1、



select Student.*



from Student , SC



where Student.SID = SC.SID



group by Student.SID , Student.Sname , Student.Sage , Student.Ssex having count(CID) < (select count(CID) from Course)



--11.2



select Student.*



from Student left join SC



on Student.SID = SC.SID



group by Student.SID , Student.Sname , Student.Sage , Student.Ssex having count(CID) < (select count(CID) from Course)



--12、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 distinct Student.* from Student , SC where Student.SID = SC.SID and SC.CID in (select CID from SC where SID = '01') and Student.SID <> '01'



--13、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 where SID in



(select distinct SC.SID from SC where SID <> '01' and SC.CID in (select distinct CID from SC where SID = '01')



group by SC.SID having count(1) = (select count(1) from SC where SID='01'))



--14、查询没学过"张三"老师讲授的任一门课程的学生姓名



select student.* from student where student.SID not in



(select distinct sc.SID from sc , course , teacher where sc.CID = course.CID and course.TID = teacher.TID and teacher.tname = '张三')



order by student.SID



--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 student.SID , student.sname , cast(avg(score) as decimal(18,2)) avg_score from student , sc



where student.SID = SC.SID and student.SID in (select SID from SC where score < 60 group by SID having count(1) >= 2)



group by student.SID , student.sname



--16、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.CID , sc.score from student , sc



where student.SID = SC.SID and sc.score < 60 and sc.CID = '01'



order by sc.score desc



--17、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



--17.1 SQL 2000 静态



select a.SID 学生编号 , a.Sname 学生姓名 ,



max(case c.Cname when '语文' then b.score else null end) 语文 ,



max(case c.Cname when '数学' then b.score else null end) 数学 ,



max(case c.Cname when '英语' then b.score else null end) 英语 ,



cast(avg(b.score) as decimal(18,2)) 平均分



from Student a



left join SC b on a.SID = b.SID



left join Course c on b.CID = c.CID



group by a.SID , a.Sname



order by 平均分 desc



--17.2 SQL 2000 动态



declare @sql nvarchar(4000)



set @sql = 'select a.SID ' + '学生编号' + ' , a.Sname ' + '学生姓名'



select @sql = @sql + ',max(case c.Cname when '''+Cname+''' then b.score else null end) '+Cname+' '



from (select distinct Cname from Course) as t



set @sql = @sql + ' , cast(avg(b.score) as decimal(18,2)) ' + '平均分' + ' from Student a left join SC b on a.SID = b.SID left join Course c on b.CID = c.CID



group by a.SID , a.Sname order by ' + '平均分' + ' desc'



exec(@sql)



--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,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



--方法1



select m.CID 课程编号 , m.Cname 课程名称 ,



max(n.score) 最高分 ,



min(n.score) 最低分 ,



cast(avg(n.score) as decimal(18,2)) 平均分 ,



cast((select count(1) from SC where CID = m.CID and score >= 60)*100.0 / (select count(1) from SC where CID = m.CID) as decimal(18,2)) 及格率 ,



cast((select count(1) from SC where CID = m.CID and score >= 70 and score < 80)*100.0 / (select count(1) from SC where CID = m.CID) as decimal(18,2)) 中等率 ,



cast((select count(1) from SC where CID = m.CID and score >= 80 and score < 90)*100.0 / (select count(1) from SC where CID = m.CID) as decimal(18,2)) 优良率 ,



cast((select count(1) from SC where CID = m.CID and score >= 90)*100.0 / (select count(1) from SC where CID = m.CID) as decimal(18,2)) 优秀率



from Course m , SC n



where m.CID = n.CID



group by m.CID , m.Cname



order by m.CID



--方法2



select m.CID 课程编号 , m.Cname 课程名称 ,



(select max(score) from SC where CID = m.CID) 最高分 ,



(select min(score) from SC where CID = m.CID) 最低分 ,



(select cast(avg(score) as decimal(18,2)) from SC where CID = m.CID) 平均分 ,



cast((select count(1) from SC where CID = m.CID and score >= 60)*100.0 / (select count(1) from SC where CID = m.CID) as decimal(18,2)) 及格率,



cast((select count(1) from SC where CID = m.CID and score >= 70 and score < 80)*100.0 / (select count(1) from SC where CID = m.CID) as decimal(18,2)) 中等率 ,



cast((select count(1) from SC where CID = m.CID and score >= 80 and score < 90)*100.0 / (select count(1) from SC where CID = m.CID) as decimal(18,2)) 优良率 ,



cast((select count(1) from SC where CID = m.CID and score >= 90)*100.0 / (select count(1) from SC where CID = m.CID) as decimal(18,2)) 优秀率



from Course m



order by m.CID



--19、按各科成绩进行排序,并显示排名



--19.1 sql 2000用子查询完成



--Score重复时保留名次空缺



select t.* , px = (select count(1) from SC where CID = t.CID and score > t.score) + 1from sc t order by t.cid , px



--Score重复时合并名次



select t.* , px = (select count(distinct score) from SC where CID = t.CID and score >= t.score) from sc t order by t.cid , px



--19.2 sql 2005用rank,DENSE_RANK完成



--Score重复时保留名次空缺(rank完成)



select t.* , px = rank() over(partition by cid order by score desc) from sc t order by t.CID , px



--Score重复时合并名次(DENSE_RANK完成)



select t.* , px = DENSE_RANK() over(partition by cid order by score desc) from sc t order by t.CID , px



--20、查询学生的总成绩并进行排名



--20.1 查询学生的总成绩



select m.SID 学生编号 ,



m.Sname 学生姓名 ,



isnull(sum(score),0) 总成绩



from Student m left join SC n on m.SID = n.SID



group by m.SID , m.Sname



order by 总成绩 desc



--20.2 查询学生的总成绩并进行排名,sql 2000用子查询完成,分总分重复时保留名次空缺和不保留名次空缺两种。



select t1.* , px = (select count(1) from



(



select m.SID 学生编号 ,



m.Sname 学生姓名 ,



isnull(sum(score),0) 总成绩



from Student m left join SC n on m.SID = n.SID



group by m.SID , m.Sname



) t2 where 总成绩 > t1.总成绩) + 1 from



(



select m.SID 学生编号 ,



m.Sname 学生姓名 ,



isnull(sum(score),0) 总成绩



from Student m left join SC n on m.SID = n.SID



group by m.SID , m.Sname



) t1



order by px



select t1.* , px = (select count(distinct 总成绩) from



(



select m.SID 学生编号 ,



m.Sname 学生姓名 ,



isnull(sum(score),0) 总成绩



from Student m left join SC n on m.SID = n.SID



group by m.SID , m.Sname



) t2 where 总成绩 >= t1.总成绩) from



(



select m.SID 学生编号 ,



m.Sname 学生姓名 ,



isnull(sum(score),0) 总成绩



from Student m left join SC n on m.SID = n.SID



group by m.SID , m.Sname



) t1



order by px



--20.3 查询学生的总成绩并进行排名,sql 2005用rank,DENSE_RANK完成,分总分重复时保留名次空缺和不保留名次空缺两种。



select t.* , px = rank() over(order by 总成绩 desc) from



(



select m.SID 学生编号 ,



m.Sname 学生姓名 ,



isnull(sum(score),0) 总成绩



from Student m left join SC n on m.SID = n.SID



group by m.SID , m.Sname



) t



order by px



select t.* , px = DENSE_RANK() over(order by 总成绩 desc) from



(



select m.SID 学生编号 ,



m.Sname 学生姓名 ,



isnull(sum(score),0) 总成绩



from Student m left join SC n on m.SID = n.SID



group by m.SID , m.Sname



) t



order by px



--21、查询不同老师所教不同课程平均分从高到低显示



select m.TID , m.Tname , cast(avg(o.score) as decimal(18,2)) avg_score



from Teacher m , Course n , SC o



where m.TID = n.TID and n.CID = o.CID



group by m.TID , m.Tname



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



--22.1 sql 2000用子查询完成



--Score重复时保留名次空缺



select * from (select t.* , px = (select count(1) from SC where CID = t.CID and score > t.score) + 1 from sc t) m where px between 2 and 3 order by m.cid , m.px



--Score重复时合并名次



select * from (select t.* , px = (select count(distinct score) from SC where CID = t.CID and score >= t.score) from sc t) m where px between 2 and 3 order by m.cid , m.px



--22.2 sql 2005用rank,DENSE_RANK完成



--Score重复时保留名次空缺(rank完成)



select * from (select t.* , px = rank() over(partition by cid order by score desc) from sc t) m where px between 2 and 3 order by m.CID , m.px



--Score重复时合并名次(DENSE_RANK完成)



select * from (select t.* , px = DENSE_RANK() over(partition by cid order by score desc) from sc t) m where px between 2 and 3 order by m.CID , m.px



--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



--23.1 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



--横向显示



select Course.CID 课程编号 , Cname as 课程名称 ,



sum(case when score >= 85 then 1 else 0 end) 85-100 ,



sum(case when score >= 70 and score < 85 then 1 else 0 end) 70-85 ,



sum(case when score >= 60 and score < 70 then 1 else 0 end) 60-70 ,



sum(case when score < 60 then 1 else 0 end) 0-60



from sc , Course



where SC.CID = Course.CID



group by Course.CID , Course.Cname



order by Course.CID



--纵向显示1(显示存在的分数段)



select m.CID 课程编号 , m.Cname 课程名称 , 分数段 = (



case when n.score >= 85 then '85-100'



when n.score >= 70 and n.score < 85 then '70-85'



when n.score >= 60 and n.score < 70 then '60-70'



else '0-60'



end) ,



count(1) 数量



from Course m , sc n



where m.CID = n.CID



group by m.CID , m.Cname , (



case when n.score >= 85 then '85-100'



when n.score >= 70 and n.score < 85 then '70-85'



when n.score >= 60 and n.score < 70 then '60-70'



else '0-60'



end)



order by m.CID , m.Cname , 分数段



--纵向显示2(显示存在的分数段,不存在的分数段用0显示)



select m.CID 课程编号 , m.Cname 课程名称 , 分数段 = (



case when n.score >= 85 then '85-100'



when n.score >= 70 and n.score < 85 then '70-85'



when n.score >= 60 and n.score < 70 then '60-70'



else '0-60'



end) ,



count(1) 数量



from Course m , sc n



where m.CID = n.CID



group by all m.CID , m.Cname , (



case when n.score >= 85 then '85-100'



when n.score >= 70 and n.score < 85 then '70-85'



when n.score >= 60 and n.score < 70 then '60-70'



else '0-60'



end)



order by m.CID , m.Cname , 分数段



--23.2 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 及所占百分比



--横向显示



select m.CID 课程编号, m.Cname 课程名称,



(select count(1) from SC where CID = m.CID and score < 60) 0-60 ,



cast((select count(1) from SC where CID = m.CID and score < 60)*100.0 / (select count(1) from SC where CID = m.CID) as decimal(18,2)) 百分比 ,



(select count(1) from SC where CID = m.CID and score >= 60 and score < 70) 60-70 ,



cast((select count(1) from SC where CID = m.CID and score >= 60 and score < 70)*100.0 / (select count(1) from SC where CID = m.CID) as decimal(18,2)) 百分比 ,



(select count(1) from SC where CID = m.CID and score >= 70 and score < 85) 70-85 ,



cast((select count(1) from SC where CID = m.CID and score >= 70 and score < 85)*100.0 / (select count(1) from SC where CID = m.CID) as decimal(18,2)) 百分比 ,



(select count(1) from SC where CID = m.CID and score >= 85) 85-100 ,



cast((select count(1) from SC where CID = m.CID and score >= 85)*100.0 / (select count(1) from SC where CID = m.CID) as decimal(18,2)) 百分比



from Course m



order by m.CID



--纵向显示1(显示存在的分数段)



select m.CID 课程编号 , m.Cname 课程名称 , 分数段 = (



case when n.score >= 85 then '85-100'



when n.score >= 70 and n.score < 85 then '70-85'



when n.score >= 60 and n.score < 70 then '60-70'



else '0-60'



end) ,



count(1) 数量 ,



cast(count(1) * 100.0 / (select count(1) from sc where CID = m.CID) as decimal(18,2)) 百分比



from Course m , sc n



where m.CID = n.CID



group by m.CID , m.Cname , (



case when n.score >= 85 then '85-100'



when n.score >= 70 and n.score < 85 then '70-85'



when n.score >= 60 and n.score < 70 then '60-70'



else '0-60'



end)



order by m.CID , m.Cname , 分数段



--纵向显示2(显示存在的分数段,不存在的分数段用0显示)



select m.CID 课程编号 , m.Cname 课程名称 , 分数段 = (



case when n.score >= 85 then '85-100'



when n.score >= 70 and n.score < 85 then '70-85'



when n.score >= 60 and n.score < 70 then '60-70'



else '0-60'



end) ,



count(1) 数量 ,



cast(count(1) * 100.0 / (select count(1) from sc where CID = m.CID) as decimal(18,2)) 百分比



from Course m , sc n



where m.CID = n.CID



group by all m.CID , m.Cname , (



case when n.score >= 85 then '85-100'



when n.score >= 70 and n.score < 85 then '70-85'



when n.score >= 60 and n.score < 70 then '60-70'



else '0-60'



end)



order by m.CID , m.Cname , 分数段



--24、查询学生平均成绩及其名次



--24.1 查询学生的平均成绩并进行排名,sql 2000用子查询完成,分平均成绩重复时保留名次空缺和不保留名次空缺两种。



select t1.* , px = (select count(1) from



(



select m.SID 学生编号 ,



m.Sname 学生姓名 ,



isnull(cast(avg(score) as decimal(18,2)),0) 平均成绩



from Student m left join SC n on m.SID = n.SID



group by m.SID , m.Sname



) t2 where 平均成绩 > t1.平均成绩) + 1 from



(



select m.SID 学生编号 ,



m.Sname 学生姓名 ,



isnull(cast(avg(score) as decimal(18,2)),0) 平均成绩



from Student m left join SC n on m.SID = n.SID



group by m.SID , m.Sname



) t1



order by px



select t1.* , px = (select count(distinct 平均成绩) from



(



select m.SID 学生编号 ,



m.Sname 学生姓名 ,



isnull(cast(avg(score) as decimal(18,2)),0) 平均成绩



from Student m left join SC n on m.SID = n.SID



group by m.SID , m.Sname



) t2 where 平均成绩 >= t1.平均成绩) from



(



select m.SID 学生编号 ,



m.Sname 学生姓名 ,



isnull(cast(avg(score) as decimal(18,2)),0) 平均成绩



from Student m left join SC n on m.SID = n.SID



group by m.SID , m.Sname



) t1



order by px



--24.2 查询学生的平均成绩并进行排名,sql 2005用rank,DENSE_RANK完成,分平均成绩重复时保留名次空缺和不保留名次空缺两种。



select t.* , px = rank() over(order by 平均成绩 desc) from



(



select m.SID 学生编号 ,



m.Sname 学生姓名 ,



isnull(cast(avg(score) as decimal(18,2)),0) 平均成绩



from Student m left join SC n on m.SID = n.SID



group by m.SID , m.Sname



) t



order by px



select t.* , px = DENSE_RANK() over(order by 平均成绩 desc) from



(



select m.SID 学生编号 ,



m.Sname 学生姓名 ,



isnull(cast(avg(score) as decimal(18,2)),0) 平均成绩



from Student m left join SC n on m.SID = n.SID



group by m.SID , m.Sname



) t



order by px



--25、查询各科成绩前三名的记录



--25.1 分数重复时保留名次空缺



select m.* , n.CID , n.score from Student m, SC n where m.SID = n.SID and n.score in



(select top 3 score from sc where CID = n.CID order by score desc) order by n.CID , n.score desc



--25.2 分数重复时不保留名次空缺,合并名次



--sql 2000用子查询实现



select * from (select t.* , px = (select count(distinct score) from SC where CID = t.CID and score >= t.score) from sc t) m where px between 1 and 3 order by m.Cid , m.px



--sql 2005用DENSE_RANK实现



select * from (select t.* , px = DENSE_RANK() over(partition by Cid order by score desc) from sc t) m where px between 1 and 3 order by m.CID , m.px



--26、查询每门课程被选修的学生数



select Cid , count(SID) 学生数 from sc group by CID



--27、查询出只有两门课程的全部学生的学号和姓名



select Student.SID , Student.Sname



from Student , SC



where Student.SID = SC.SID



group by Student.SID , Student.Sname



having count(SC.CID) = 2



order by Student.SID



--28、查询男生、女生人数



select count(Ssex) as 男生人数 from Student where Ssex = N'男'



select count(Ssex) as 女生人数 from Student where Ssex = N'女'



select sum(case when Ssex = N'男' then 1 else 0 end) 男生人数 ,sum(case when Ssex = N'女' then 1 else 0 end) 女生人数 from student



select case when Ssex = N'男' then N'男生人数' else N'女生人数' end 男女情况 , count(1) 人数 from student group by case when Ssex = N'男' then N'男生人数' else N'女生人数' end



--29、查询名字中含有"风"字的学生信息



select * from student where sname like N'%风%'



select * from student where charindex(N'风' , sname) > 0



--30、查询同名同性学生名单,并统计同名人数



select Sname 学生姓名 , count(*) 人数 from Student group by Sname having count(*) > 1



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



select * from Student where year(sage) = 1990



select * from Student where datediff(yy,sage,'1990-01-01') = 0



select * from Student where datepart(yy,sage) = 1990



select * from Student where convert(varchar(4),sage,120) = '1990'



--32、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 m.CID , m.Cname , cast(avg(n.score) as decimal(18,2)) avg_score



from Course m, SC n



where m.CID = n.CID



group by m.CID , m.Cname



order by avg_score desc, m.CID asc



--33、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 , a.Sname , cast(avg(b.score) as decimal(18,2)) avg_score



from Student a , sc b



where a.SID = b.SID



group by a.SID , a.Sname



having cast(avg(b.score) as decimal(18,2)) >= 85



order by a.SID



--34、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 , SC , Course



where SC.SID = Student.SID and SC.CID = Course.CID and Course.Cname = N'数学' and score < 60



--35、查询所有学生的课程及分数情况;



select Student.* , Course.Cname , SC.CID , SC.score



from Student, SC , Course



where Student.SID = SC.SID and SC.CID = Course.CID



order by Student.SID , SC.CID



--36、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.* , Course.Cname , SC.CID , SC.score



from Student, SC , Course



where Student.SID = SC.SID and SC.CID = Course.CID and SC.score >= 70



order by Student.SID , SC.CID



--37、查询不及格的课程



select Student.* , Course.Cname , SC.CID , SC.score



from Student, SC , Course



where Student.SID = SC.SID and SC.CID = Course.CID and SC.score < 60



order by Student.SID , SC.CID



--38、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.* , Course.Cname , SC.CID , SC.score



from Student, SC , Course



where Student.SID = SC.SID and SC.CID = Course.CID and SC.CID = '01' and SC.score >= 80



order by Student.SID , SC.CID



--39、求每门课程的学生人数



select Course.CID , Course.Cname , count(*) 学生人数



from Course , SC



where Course.CID = SC.CID



group by Course.CID , Course.Cname



order by Course.CID , Course.Cname



--40、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



--40.1 当最高分只有一个时



select top 1 Student.* , Course.Cname , SC.CID , SC.score



from Student, SC , Course , Teacher



where Student.SID = SC.SID and SC.CID = Course.CID and Course.TID = Teacher.TID and Teacher.Tname = N'张三'



order by SC.score desc



--40.2 当最高分出现多个时



select Student.* , Course.Cname , SC.CID , SC.score



from Student, SC , Course , Teacher



where Student.SID = SC.SID and SC.CID = Course.CID and Course.TID = Teacher.TID and Teacher.Tname = N'张三' and



SC.score = (select max(SC.score) from SC , Course , Teacher where SC.CID = Course.CID and Course.TID = Teacher.TID and Teacher.Tname = N'张三')



--41、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



--方法1



select m.* from SC m ,(select CID , score from SC group by CID , score having count(1) > 1) n



where m.CID= n.CID and m.score = n.score order by m.CID , m.score , m.SID



--方法2



select m.* from SC m where exists (select 1 from (select CID , score from SC group by CID , score having count(1) > 1) n



where m.CID= n.CID and m.score = n.score) order by m.CID , m.score , m.SID



--42、查询每门功成绩最好的前两名



select t.* from sc t where score in (select top 2 score from sc where CID = T.CID order by score desc) order by t.CID , t.score desc



--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 Course.CID , Course.Cname , count(*) 学生人数



from Course , SC



where Course.CID = SC.CID



group by Course.CID , Course.Cname



having count(*) >= 5



order by 学生人数 desc , Course.CID



--44、检索至少选修两门课程的学生学号



select student.SID , student.Sname



from student , SC



where student.SID = SC.SID



group by student.SID , student.Sname



having count(1) >= 2



order by student.SID



--45、查询选修了全部课程的学生信息



--方法1 根据数量来完成



select student.* from student where SID in



(select SID from sc group by SID having count(1) = (select count(1) from course))



--方法2 使用双重否定来完成



select t.* from student t where t.SID not in



(



select distinct m.SID from



(



select SID , CID from student , course



) m where not exists (select 1 from sc n where n.SID = m.SID and n.CID = m.CID)



)



--方法3 使用双重否定来完成



select t.* from student t where not exists(select 1 from



(



select distinct m.SID from



(



select SID , CID from student , course



) m where not exists (select 1 from sc n where n.SID = m.SID and n.CID = m.CID)



) k where k.SID = t.SID



)



--46、查询各学生的年龄



--46.1 只按照年份来算



select * , datediff(yy , sage , getdate()) 年龄 from student



--46.2 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 * , case when right(convert(varchar(10),getdate(),120),5) < right(convert(varchar(10),sage,120),5) then datediff(yy , sage , getdate()) - 1 else datediff(yy , sage , getdate()) end 年龄 from student



--47、查询本周过生日的学生



select * from student where datediff(week,datename(yy,getdate()) + right(convert(varchar(10),sage,120),6),getdate()) = 0



--48、查询下周过生日的学生



select * from student where datediff(week,datename(yy,getdate()) + right(convert(varchar(10),sage,120),6),getdate()) = -1



--49、查询本月过生日的学生



select * from student where datediff(mm,datename(yy,getdate()) + right(convert(varchar(10),sage,120),6),getdate()) = 0



--50、查询下月过生日的学生



select * from student where datediff(mm,datename(yy,getdate()) + right(convert(varchar(10),sage,120),6),getdate()) = -1



drop table Student,Course,Teacher,SC





 


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