标题：一个项目涉及到的50个Sql语句(整理版)
说明：以下五十个语句都按照测试数据进行过测试，最好每次只单独运行一个语句。
问题及描述：
--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
createtable Student(S# varchar(10),Sname nvarchar(10),Sage datetime,Ssex nvarchar(10))
insertinto Student values(‘01‘ , N‘赵雷‘ , ‘1990-01-01‘ , N‘男‘)
insertinto Student values(‘02‘ , N‘钱电‘ , ‘1990-12-21‘ , N‘男‘)
insertinto Student values(‘03‘ , N‘孙风‘ , ‘1990-05-20‘ , N‘男‘)
insertinto Student values(‘04‘ , N‘李云‘ , ‘1990-08-06‘ , N‘男‘)
insertinto Student values(‘05‘ , N‘周梅‘ , ‘1991-12-01‘ , N‘女‘)
insertinto Student values(‘06‘ , N‘吴兰‘ , ‘1992-03-01‘ , N‘女‘)
insertinto Student values(‘07‘ , N‘郑竹‘ , ‘1989-07-01‘ , N‘女‘)
insertinto Student values(‘08‘ , N‘王菊‘ , ‘1990-01-20‘ , N‘女‘)
createtable Course(C# varchar(10),Cname nvarchar(10),T# varchar(10))
insertinto Course values(‘01‘ , N‘语文‘ , ‘02‘)
insertinto Course values(‘02‘ , N‘数学‘ , ‘01‘)
insertinto Course values(‘03‘ , N‘英语‘ , ‘03‘)
createtable Teacher(T# varchar(10),Tname nvarchar(10))
insertinto Teacher values(‘01‘ , N‘张三‘)
insertinto Teacher values(‘02‘ , N‘李四‘)
insertinto Teacher values(‘03‘ , N‘王五‘)
createtable SC(S# varchar(10),C# varchar(10),score decimal(18,1))
insertinto SC values(‘01‘ , ‘01‘ , 80)
insertinto SC values(‘01‘ , ‘02‘ , 90)
insertinto SC values(‘01‘ , ‘03‘ , 99)
insertinto SC values(‘02‘ , ‘01‘ , 70)
insertinto SC values(‘02‘ , ‘02‘ , 60)
insertinto SC values(‘02‘ , ‘03‘ , 80)
insertinto SC values(‘03‘ , ‘01‘ , 80)
insertinto SC values(‘03‘ , ‘02‘ , 80)
insertinto SC values(‘03‘ , ‘03‘ , 80)
insertinto SC values(‘04‘ , ‘01‘ , 50)
insertinto SC values(‘04‘ , ‘02‘ , 30)
insertinto SC values(‘04‘ , ‘03‘ , 20)
insertinto SC values(‘05‘ , ‘01‘ , 76)
insertinto SC values(‘05‘ , ‘02‘ , 87)
insertinto SC values(‘06‘ , ‘01‘ , 31)
insertinto SC values(‘06‘ , ‘03‘ , 34)
insertinto SC values(‘07‘ , ‘02‘ , 89)
insertinto 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
leftjoin SC b on a.S# = b.S# and b.C# =‘01‘
leftjoin 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
leftjoin SC b on a.S# = b.S# and b.C# =‘01‘
leftjoin SC c on a.S# = c.S# and c.C# =‘02‘
whereisnull(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) asdecimal(18,2)) avg_score
from Student a , sc b
where a.S# = b.S#
groupby a.S# , a.Sname
havingcast(avg(b.score) asdecimal(18,2)) >=60
orderby 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) asdecimal(18,2)) avg_score
from Student a , sc b
where a.S# = b.S#
groupby a.S# , a.Sname
havingcast(avg(b.score) asdecimal(18,2)) <60
orderby 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) asdecimal(18,2)),0) avg_score
from Student a leftjoin sc b
on a.S# = b.S#
groupby a.S# , a.Sname
havingisnull(cast(avg(b.score) asdecimal(18,2)),0) <60
orderby 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#
groupby a.S#,a.Sname
orderby 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 leftjoin SC b
on a.S# = b.S#
groupby a.S#,a.Sname
orderby a.S#

--6、查询"李"姓老师的数量
--方法1
selectcount(Tname) ["李"姓老师的数量]from Teacher where Tname like N‘李%‘
--方法2
selectcount(Tname) ["李"姓老师的数量]from Teacher whereleft(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
selectdistinct 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‘
orderby 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# notin (selectdistinct SC.S# from SC , Course , Teacher where SC.C# = Course.C# and Course.T# = Teacher.T# and Teacher.Tname = N‘张三‘) orderby 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‘andexists (Select1from SC SC_2 where SC_2.S# = SC.S# and SC_2.C# =‘02‘) orderby Student.S#
--方法2
select Student.*from Student , SC where Student.S# = SC.S# and SC.C# =‘02‘andexists (Select1from SC SC_2 where SC_2.S# = SC.S# and SC_2.C# =‘01‘) orderby Student.S#
--方法3
select m.*from Student m where S# in
(
  select S# from
  (
    selectdistinct S# from SC where C# =‘01‘
    unionall
    selectdistinct S# from SC where C# =‘02‘
  ) t groupby S# havingcount(1) =2
)
orderby 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‘andnotexists (Select1from SC SC_2 where SC_2.S# = SC.S# and SC_2.C# =‘02‘) orderby Student.S#
--方法2
select Student.*from Student , SC where Student.S# = SC.S# and SC.C# =‘01‘and Student.S# notin (Select SC_2.S# from SC SC_2 where SC_2.S# = SC.S# and SC_2.C# =‘02‘) orderby 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#
groupby Student.S# , Student.Sname , Student.Sage , Student.Ssex havingcount(C#) < (selectcount(C#) from Course)
--11.2
select Student.*
from Student leftjoin SC
on Student.S# = SC.S#
groupby Student.S# , Student.Sname , Student.Sage , Student.Ssex havingcount(C#) < (selectcount(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
selectdistinct 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
(selectdistinct SC.S# from SC where S# <>‘01‘and SC.C# in (selectdistinct C# from SC where S# =‘01‘)
groupby SC.S# havingcount(1) = (selectcount(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# notin
(selectdistinct sc.S# from sc , course , teacher where sc.C# = course.C# and course.T# = teacher.T# and teacher.tname = N‘张三‘)
orderby 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) asdecimal(18,2)) avg_score from student , sc
where student.S# = SC.S# and student.S# in (select S# from SC where score <60groupby S# havingcount(1) >=2)
groupby 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 <60and sc.C# =‘01‘
orderby 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 elsenullend) [语文],
       max(case c.Cname when N‘数学‘then b.score elsenullend) [数学],
       max(case c.Cname when N‘英语‘then b.score elsenullend) [英语],
       cast(avg(b.score) asdecimal(18,2)) 平均分
from Student a
leftjoin SC b on a.S# = b.S#
leftjoin Course c on b.C# = c.C#
groupby a.S# , a.Sname
orderby 平均分 desc
--17.2 SQL 2000 动态
declare@sqlnvarchar(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 (selectdistinct 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) asdecimal(18,2)) [平均分],
  cast((selectcount(1) from SC where C# = m.C# and score >=60)*100.0/ (selectcount(1) from SC where C# = m.C#) asdecimal(18,2)) [及格率(%)],
  cast((selectcount(1) from SC where C# = m.C# and score >=70and score <80 )*100.0/ (selectcount(1) from SC where C# = m.C#) asdecimal(18,2)) [中等率(%)],
  cast((selectcount(1) from SC where C# = m.C# and score >=80and score <90 )*100.0/ (selectcount(1) from SC where C# = m.C#) asdecimal(18,2)) [优良率(%)],
  cast((selectcount(1) from SC where C# = m.C# and score >=90)*100.0/ (selectcount(1) from SC where C# = m.C#) asdecimal(18,2)) [优秀率(%)]
from Course m , SC n
where m.C# = n.C#
groupby m.C# , m.Cname
orderby m.C#
--方法2
select m.C# [课程编号], m.Cname [课程名称],
  (selectmax(score) from SC where C# = m.C#) [最高分],
  (selectmin(score) from SC where C# = m.C#) [最低分],
  (selectcast(avg(score) asdecimal(18,2)) from SC where C# = m.C#) [平均分],
  cast((selectcount(1) from SC where C# = m.C# and score >=60)*100.0/ (selectcount(1) from SC where C# = m.C#) asdecimal(18,2)) [及格率(%)],
  cast((selectcount(1) from SC where C# = m.C# and score >=70and score <80 )*100.0/ (selectcount(1) from SC where C# = m.C#) asdecimal(18,2)) [中等率(%)],
  cast((selectcount(1) from SC where C# = m.C# and score >=80and score <90 )*100.0/ (selectcount(1) from SC where C# = m.C#) asdecimal(18,2)) [优良率(%)],
  cast((selectcount(1) from SC where C# = m.C# and score >=90)*100.0/ (selectcount(1) from SC where C# = m.C#) asdecimal(18,2)) [优秀率(%)]
from Course m
orderby 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 = (selectcount(1) from SC where C# = t.C# and score > t.score) +1from sc t orderby t.c# , px
--Score重复时合并名次
select t.* , px = (selectcount(distinct score) from SC where C# = t.C# and score >= t.score) from sc t orderby 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# orderby score desc) from sc t orderby t.C# , px
--Score重复时合并名次(DENSE_RANK完成)
select t.* , px = DENSE_RANK() over(partition by c# orderby score desc) from sc t orderby 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 leftjoin SC n on m.S# = n.S#
groupby m.S# , m.Sname
orderby[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 = (selectcount(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 leftjoin SC n on m.S# = n.S#
  groupby m.S# , m.Sname
) t2 where 总成绩 > t1.总成绩) +1from
(
  select m.S# [学生编号] ,
         m.Sname [学生姓名] ,
         isnull(sum(score),0) [总成绩]
  from Student m leftjoin SC n on m.S# = n.S#
  groupby m.S# , m.Sname
) t1
orderby px

select t1.* , px = (selectcount(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 leftjoin SC n on m.S# = n.S#
  groupby 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 leftjoin SC n on m.S# = n.S#
  groupby m.S# , m.Sname
) t1
orderby 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(orderby[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 leftjoin SC n on m.S# = n.S#
  groupby m.S# , m.Sname
) t
orderby px

select t.* , px = DENSE_RANK() over(orderby[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 leftjoin SC n on m.S# = n.S#
  groupby m.S# , m.Sname
) t
orderby 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) asdecimal(18,2)) avg_score
from Teacher m , Course n , SC o
where m.T# = n.T# and n.C# = o.C#
groupby m.T# , m.Tname
orderby 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 = (selectcount(1) from SC where C# = t.C# and score > t.score) +1from sc t) m where px between2and3orderby m.c# , m.px
--Score重复时合并名次
select*from (select t.* , px = (selectcount(distinct score) from SC where C# = t.C# and score >= t.score) from sc t) m where px between2and3orderby 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# orderby score desc) from sc t) m where px between2and3orderby 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# orderby score desc) from sc t) m where px between2and3orderby 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(casewhen score >=85then1else0end) [85-100],
  sum(casewhen score >=70and score <85then1else0end) [70-85],
  sum(casewhen score >=60and score <70then1else0end) [60-70],
  sum(casewhen score <60then1else0end) [0-60]
from sc , Course
where SC.C# = Course.C#
groupby Course.C# , Course.Cname
orderby 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 = (
  casewhen n.score >=85then‘85-100‘
       when n.score >=70and n.score <85then‘70-85‘
       when n.score >=60and n.score <70then‘60-70‘
       else‘0-60‘
  end) ,
  count(1) 数量
from Course m , sc n
where m.C# = n.C#
groupby m.C# , m.Cname , (
  casewhen n.score >=85then‘85-100‘
       when n.score >=70and n.score <85then‘70-85‘
       when n.score >=60and n.score <70then‘60-70‘
       else‘0-60‘
  end)
orderby 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 = (
  casewhen n.score >=85then‘85-100‘
       when n.score >=70and n.score <85then‘70-85‘
       when n.score >=60and n.score <70then‘60-70‘
       else‘0-60‘
  end) ,
  count(1) 数量
from Course m , sc n
where m.C# = n.C#
groupbyall m.C# , m.Cname , (
  casewhen n.score >=85then‘85-100‘
       when n.score >=70and n.score <85then‘70-85‘
       when n.score >=60and n.score <70then‘60-70‘
       else‘0-60‘
  end)
orderby 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,
  (selectcount(1) from SC where C# = m.C# and score <60) [0-60],
  cast((selectcount(1) from SC where C# = m.C# and score <60)*100.0/ (selectcount(1) from SC where C# = m.C#) asdecimal(18,2)) [百分比(%)],
  (selectcount(1) from SC where C# = m.C# and score >=60and score <70) [60-70],
  cast((selectcount(1) from SC where C# = m.C# and score >=60and score <70)*100.0/ (selectcount(1) from SC where C# = m.C#) asdecimal(18,2)) [百分比(%)],
  (selectcount(1) from SC where C# = m.C# and score >=70and score <85) [70-85],
  cast((selectcount(1) from SC where C# = m.C# and score >=70and score <85)*100.0/ (selectcount(1) from SC where C# = m.C#) asdecimal(18,2)) [百分比(%)],
  (selectcount(1) from SC where C# = m.C# and score >=85) [85-100],
  cast((selectcount(1) from SC where C# = m.C# and score >=85)*100.0/ (selectcount(1) from SC where C# = m.C#) asdecimal(18,2)) [百分比(%)]
from Course m
orderby 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 = (
  casewhen n.score >=85then‘85-100‘
       when n.score >=70and n.score <85then‘70-85‘
       when n.score >=60and n.score <70then‘60-70‘
       else‘0-60‘
  end) ,
  count(1) 数量 , 
  cast(count(1) *100.0/ (selectcount(1) from sc where C# = m.C#) asdecimal(18,2)) [百分比(%)]
from Course m , sc n
where m.C# = n.C#
groupby m.C# , m.Cname , (
  casewhen n.score >=85then‘85-100‘
       when n.score >=70and n.score <85then‘70-85‘
       when n.score >=60and n.score <70then‘60-70‘
       else‘0-60‘
  end)
orderby 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 = (
  casewhen n.score >=85then‘85-100‘
       when n.score >=70and n.score <85then‘70-85‘
       when n.score >=60and n.score <70then‘60-70‘
       else‘0-60‘
  end) ,
  count(1) 数量 , 
  cast(count(1) *100.0/ (selectcount(1) from sc where C# = m.C#) asdecimal(18,2)) [百分比(%)]
from Course m , sc n
where m.C# = n.C#
groupbyall m.C# , m.Cname , (
  casewhen n.score >=85then‘85-100‘
       when n.score >=70and n.score <85then‘70-85‘
       when n.score >=60and n.score <70then‘60-70‘
       else‘0-60‘
  end)
orderby 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 = (selectcount(1) from
(
  select m.S# [学生编号] ,
         m.Sname [学生姓名] ,
         isnull(cast(avg(score) asdecimal(18,2)),0) [平均成绩]
  from Student m leftjoin SC n on m.S# = n.S#
  groupby m.S# , m.Sname
) t2 where 平均成绩 > t1.平均成绩) +1from
(
  select m.S# [学生编号] ,
         m.Sname [学生姓名] ,
         isnull(cast(avg(score) asdecimal(18,2)),0) [平均成绩]
  from Student m leftjoin SC n on m.S# = n.S#
  groupby m.S# , m.Sname
) t1
orderby px

select t1.* , px = (selectcount(distinct 平均成绩) from
(
  select m.S# [学生编号] ,
         m.Sname [学生姓名] ,
         isnull(cast(avg(score) asdecimal(18,2)),0) [平均成绩]
  from Student m leftjoin SC n on m.S# = n.S#
  groupby 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) asdecimal(18,2)),0) [平均成绩]
  from Student m leftjoin SC n on m.S# = n.S#
  groupby m.S# , m.Sname
) t1
orderby 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(orderby[平均成绩]desc) from
(
  select m.S# [学生编号] ,
         m.Sname [学生姓名] ,
         isnull(cast(avg(score) asdecimal(18,2)),0) [平均成绩]
  from Student m leftjoin SC n on m.S# = n.S#
  groupby m.S# , m.Sname
) t
orderby px

select t.* , px = DENSE_RANK() over(orderby[平均成绩]desc) from
(
  select m.S# [学生编号] ,
         m.Sname [学生姓名] ,
         isnull(cast(avg(score) asdecimal(18,2)),0) [平均成绩]
  from Student m leftjoin SC n on m.S# = n.S#
  groupby m.S# , m.Sname
) t
orderby 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
(selecttop3 score from sc where C# = n.C# orderby score desc) orderby 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 = (selectcount(distinct score) from SC where C# = t.C# and score >= t.score) from sc t) m where px between1and3orderby m.c# , m.px
--sql 2005用DENSE_RANK实现
select*from (select t.* , px = DENSE_RANK() over(partition by c# orderby score desc) from sc t) m where px between1and3orderby 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 groupby 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#
groupby Student.S# , Student.Sname
havingcount(SC.C#) =2
orderby Student.S#

--28、查询男生、女生人数
selectcount(Ssex) as 男生人数 from Student where Ssex = N‘男‘
selectcount(Ssex) as 女生人数 from Student where Ssex = N‘女‘
selectsum(casewhen Ssex = N‘男‘then1else0end) [男生人数],sum(casewhen Ssex = N‘女‘then1else0end) [女生人数]from student
selectcasewhen 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 groupbycasewhen 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 wherecharindex(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 groupby Sname havingcount(*) >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 whereyear(sage) =1990
select*from Student wheredatediff(yy,sage,‘1990-01-01‘) =0
select*from Student wheredatepart(yy,sage) =1990
select*from Student whereconvert(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) asdecimal(18,2)) avg_score
from Course m, SC n
where m.C# = n.C#   
groupby m.C# , m.Cname
orderby 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) asdecimal(18,2)) avg_score
from Student a , sc b
where a.S# = b.S#
groupby a.S# , a.Sname
havingcast(avg(b.score) asdecimal(18,2)) >=85
orderby 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#
orderby 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
orderby 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
orderby 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
orderby 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#
groupby  Course.C# , Course.Cname
orderby 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
selecttop1 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‘
orderby 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 = (selectmax(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 groupby C# , score havingcount(1) >1) n
where m.C#= n.C# and m.score = n.score orderby m.C# , m.score , m.S#
--方法2
select m.*from SC m whereexists (select1from (select C# , score from SC groupby C# , score havingcount(1) >1) n
where m.C#= n.C# and m.score = n.score) orderby 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 (selecttop2 score from sc where C# = T.C# orderby score desc) orderby 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#
groupby  Course.C# , Course.Cname
havingcount(*) >=5
orderby[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#
groupby student.S# , student.Sname
havingcount(1) >=2
orderby 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 groupby S# havingcount(1) = (selectcount(1) from course))
--方法2 使用双重否定来完成
select t.*from student t where t.S# notin
(
  selectdistinct m.S# from
  (
    select S# , C# from student , course
  ) m wherenotexists (select1from 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 wherenotexists(select1from
(
  selectdistinct m.S# from
  (
    select S# , C# from student , course
  ) m wherenotexists (select1from 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* , casewhenright(convert(varchar(10),getdate(),120),5) <right(convert(varchar(10),sage,120),5) thendatediff(yy , sage , getdate()) -1elsedatediff(yy , sage , getdate()) end[年龄]from student

--47、查询本周过生日的学生
select*from student wheredatediff(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 wheredatediff(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 wheredatediff(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 wheredatediff(mm,datename(yy,getdate()) +right(convert(varchar(10),sage,120),6),getdate()) =-1

droptable  Student,Course,Teacher,SC

一个项目涉及到的50个Sql语句