一个标准的项目SQL应用范例

--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')
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)》。

 

--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