50个经典Sql语句

50个经典Sql语句

--1.学生表

Student(S,Sname,Sage,Ssex) --S 学生编号,Sname 学生姓名,Sage 出生年月,Ssex 学生性别

--2.课程表 

Course(C,Cname,T) --C --课程编号,Cname 课程名称,T 教师编号

--3.教师表 

Teacher(T,Tname) --T 教师编号,Tname 教师姓名

--4.成绩表 

SC(S,C,score) --S 学生编号,C 课程编号,score 分数

*/

--创建测试数据

create table Student(S varchar(10),Sname nvarchar(10),Sage datetime,Ssex nvarchar(10))

insert into Student values('01' , N'赵雷' , '1990-01-01' , N'男')

insert into Student values('02' , N'钱电' , '1990-12-21' , N'男')

insert into Student values('03' , N'孙风' , '1990-05-20' , N'男')

insert into Student values('04' , N'李云' , '1990-08-06' , N'男')

insert into Student values('05' , N'周梅' , '1991-12-01' , N'女')

insert into Student values('06' , N'吴兰' , '1992-03-01' , N'女')

insert into Student values('07' , N'郑竹' , '1989-07-01' , N'女')

insert into Student values('08' , N'王菊' , '1990-01-20' , N'女')

create table Course(C varchar(10),Cname nvarchar(10),T 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')

create table Teacher(T varchar(10),Tname nvarchar(10))

insert into Teacher values('01' , N'张三')

insert into Teacher values('02' , N'李四')

insert into Teacher values('03' , N'王五')

create table SC(S varchar(10),C 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)

go



--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.S = b.S and a.S = c.S and b.C = '01' and c.C = '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.S = b.S and b.C = '01'

left join SC c on a.S = c.S and c.C = '02'

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



--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.S = b.S and a.S = c.S and b.C = '01' and c.C = '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.S = b.S and b.C = '01'

left join SC c on a.S = c.S and c.C = '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.S , a.Sname , cast(avg(b.score) as decimal(18,2)) avg_score

from Student a , sc b

where a.S = b.S

group by a.S , a.Sname

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

order by a.S



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

from Student a , sc b

where a.S = b.S

group by a.S , a.Sname

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

order by a.S

--4.2、查询在sc表中不存在成绩的学生信息的SQL语句。

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

from Student a left join sc b

on a.S = b.S

group by a.S , a.Sname

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

order by a.S



--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.S [学生编号], a.Sname [学生姓名], count(b.C) 选课总数, sum(score) [所有课程的总成绩]

from Student a , SC b 

where a.S = b.S 

group by a.S,a.Sname 

order by a.S

--5.2、查询所有(包括有成绩和无成绩)的SQL。

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

from Student a left join SC b 

on a.S = b.S 

group by a.S,a.Sname 

order by a.S



--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 N'李%'

--方法2

select count(Tname) ["李"姓老师的数量] from Teacher where left(Tname,1) = N'李'

/*

"李"姓老师的数量   

----------- 

1

*/



--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.S = SC.S and SC.C = Course.C and Course.T = Teacher.T and Teacher.Tname = N'张三'

order by Student.S



--8、查询没学过"张三"老师授课的同学的信息 

select m.* from Student m where S not in (select distinct SC.S from SC , Course , Teacher where SC.C = Course.C and Course.T = Teacher.T and Teacher.Tname = N'张三') order by m.S



--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.S = SC.S and SC.C = '01' and exists (Select 1 from SC SC_2 where SC_2.S = SC.S and SC_2.C = '02') order by Student.S

--方法2

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

--方法3

select m.* from Student m where S in

(

  select S from

  (

    select distinct S from SC where C = '01'

    union all

    select distinct S from SC where C = '02'

  ) t group by S having count(1) = 2 

)

order by m.S



--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.S = SC.S and SC.C = '01' and not exists (Select 1 from SC SC_2 where SC_2.S = SC.S and SC_2.C = '02') order by Student.S

--方法2

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



--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.S = SC.S 

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

--11.2

select Student.*

from Student left join SC 

on Student.S = SC.S 

group by Student.S , Student.Sname , Student.Sage , Student.Ssex having count(C) < (select count(C) 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.S = SC.S and SC.C in (select C from SC where S = '01') and Student.S <> '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 S in

(select distinct SC.S from SC where S <> '01' and SC.C in (select distinct C from SC where S = '01') 

group by SC.S having count(1) = (select count(1) from SC where S='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.S not in 

(select distinct sc.S from sc , course , teacher where sc.C = course.C and course.T = teacher.T and teacher.tname = N'张三')

order by student.S



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

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

group by student.S , 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.C , sc.score from student , sc 

where student.S = SC.S and sc.score < 60 and sc.C = '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.S 学生编号 , a.Sname 学生姓名 ,

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

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

       max(case c.Cname when N'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.S = b.S

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

group by a.S , a.Sname

order by 平均分 desc

--17.2 SQL 2000 动态 

declare @sql nvarchar(4000)

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

select @sql = @sql + ',max(case c.Cname when N'''+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)) ' + N'平均分' + ' from Student a left join SC b on a.S = b.S left join Course c on b.C = c.C

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

exec(@sql)

--17.3 有关sql 2005的动静态写法参见我的文章《普通行列转换(version 2.0)》或《普通行列转换(version 3.0)》。







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#1楼 得分：0回复于：2010-05-17 17:47:07

SQL code

--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.C [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 C = m.C and score >= 60)*100.0 / (select count(1) from SC where C = m.C) as decimal(18,2)) [及格率(%)],

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

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

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

from Course m , SC n

where m.C = n.C

group by m.C , m.Cname

order by m.C

--方法2

select m.C [课程编号], m.Cname [课程名称], 

  (select max(score) from SC where C = m.C) [最高分],

  (select min(score) from SC where C = m.C) [最低分],

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

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

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

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

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

from Course m 

order by m.C



--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 C = t.C and score > t.score) + 1 from sc t order by t.C , px 

--Score重复时合并名次

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

--Score重复时合并名次(DENSE_RANK完成)

select t.* , px = DENSE_RANK() over(partition by C order by score desc) from sc t order by t.C , 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.S [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.S = n.S 

group by m.S , 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.S [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.S = n.S 

  group by m.S , m.Sname

) t2 where 总成绩 > t1.总成绩) + 1 from 

(

  select m.S [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.S = n.S 

  group by m.S , m.Sname

) t1

order by px



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

(

  select m.S [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.S = n.S 

  group by m.S , m.Sname

) t2 where 总成绩 >= t1.总成绩) from 

(

  select m.S [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.S = n.S 

  group by m.S , 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.S [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.S = n.S 

  group by m.S , m.Sname

) t

order by px



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

(

  select m.S [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.S = n.S 

  group by m.S , 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.T , m.Tname , cast(avg(o.score) as decimal(18,2)) avg_score

from Teacher m , Course n , SC o

where m.T = n.T and n.C = o.C

group by m.T , 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 C = t.C and score > t.score) + 1 from sc t) m where px between 2 and 3 order by m.C , m.px 

--Score重复时合并名次

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

--Score重复时合并名次(DENSE_RANK完成)

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

group by Course.C , Course.Cname

order by Course.C

--纵向显示1(显示存在的分数段)

select m.C [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.C = n.C 

group by m.C , 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.C , 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.C [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.C = n.C 

group by all m.C , 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.C , 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.C 课程编号, m.Cname 课程名称,

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

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

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

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

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

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

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

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

from Course m 

order by m.C

--纵向显示1(显示存在的分数段)

select m.C [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 C = m.C) as decimal(18,2)) [百分比(%)]

from Course m , sc n

where m.C = n.C 

group by m.C , 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.C , 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.C [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 C = m.C) as decimal(18,2)) [百分比(%)]

from Course m , sc n

where m.C = n.C 

group by all m.C , 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.C , m.Cname , 分数段



 



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#2楼 得分：0回复于：2010-05-17 17:47:22

SQL code

--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.S [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.S = n.S 

  group by m.S , m.Sname

) t2 where 平均成绩 > t1.平均成绩) + 1 from 

(

  select m.S [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.S = n.S 

  group by m.S , m.Sname

) t1

order by px



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

(

  select m.S [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.S = n.S 

  group by m.S , m.Sname

) t2 where 平均成绩 >= t1.平均成绩) from 

(

  select m.S [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.S = n.S 

  group by m.S , 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.S [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.S = n.S 

  group by m.S , m.Sname

) t

order by px



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

(

  select m.S [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.S = n.S 

  group by m.S , 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.C , n.score from Student m, SC n where m.S = n.S and n.score in 

(select top 3 score from sc where C = n.C order by score desc) order by n.C , 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 C = t.C and score >= t.score) from sc t) m where px between 1 and 3 order by m.C , m.px 

--sql 2005用DENSE_RANK实现

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



--26、查询每门课程被选修的学生数 

select C , count(S)[学生数] from sc group by C



--27、查询出只有两门课程的全部学生的学号和姓名 

select Student.S , Student.Sname

from Student , SC 

where Student.S = SC.S 

group by Student.S , Student.Sname

having count(SC.C) = 2

order by Student.S

 

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

from Course m, SC n 

where m.C = n.C    

group by m.C , m.Cname 

order by avg_score desc, m.C 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.S , a.Sname , cast(avg(b.score) as decimal(18,2)) avg_score

from Student a , sc b

where a.S = b.S

group by a.S , a.Sname

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

order by a.S



--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.S = Student.S and SC.C = Course.C 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.C , SC.score  

from Student, SC , Course 

where Student.S = SC.S and SC.C = Course.C 

order by Student.S , SC.C



--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.C , SC.score  

from Student, SC , Course 

where Student.S = SC.S and SC.C = Course.C and SC.score >= 70 

order by Student.S , SC.C 



--37、查询不及格的课程

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

from Student, SC , Course 

where Student.S = SC.S and SC.C = Course.C and SC.score < 60 

order by Student.S , SC.C 



--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.C , SC.score  

from Student, SC , Course 

where Student.S = SC.S and SC.C = Course.C and SC.C = '01' and SC.score >= 80 

order by Student.S , SC.C 



--39、求每门课程的学生人数 

select Course.C , Course.Cname , count(*) [学生人数]

from Course , SC 

where Course.C = SC.C

group by  Course.C , Course.Cname

order by Course.C , 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.C , SC.score  

from Student, SC , Course , Teacher

where Student.S = SC.S and SC.C = Course.C and Course.T = Teacher.T 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.C , SC.score  

from Student, SC , Course , Teacher

where Student.S = SC.S and SC.C = Course.C and Course.T = Teacher.T and Teacher.Tname = N'张三' and

SC.score = (select max(SC.score) from SC , Course , Teacher where SC.C = Course.C and Course.T = Teacher.T 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 C , score from SC group by C , score having count(1) > 1) n 

where m.C= n.C and m.score = n.score order by m.C , m.score , m.S

--方法2

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

where m.C= n.C and m.score = n.score) order by m.C , m.score , m.S



--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 C = T.C order by score desc) order by t.C , 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.C , Course.Cname , count(*) [学生人数]

from Course , SC 

where Course.C = SC.C

group by  Course.C , Course.Cname

having count(*) >= 5

order by [学生人数] desc , Course.C 



--44、检索至少选修两门课程的学生学号 

select student.S , student.Sname 

from student , SC 

where student.S = SC.S 

group by student.S , student.Sname 

having count(1) >= 2

order by student.S 



--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 S in

(select S from sc group by S 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.S not in 

(

  select distinct m.S from

  (

    select S , C from student , course 

  ) m where not exists (select 1 from sc n where n.S = m.S and n.C = m.C)

)

--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.S from

  (

    select S , C from student , course 

  ) m where not exists (select 1 from sc n where n.S = m.S and n.C = m.C)

) k where k.S = t.S

)



--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