[Java面试十一]数据库总结.

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)) ;
i n sert 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)

--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 0 2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) +   1   from 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

原文：http://www.cnblogs.com/wang-meng/p/5702015.html