一个项目SQL2

--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

--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