一个项目涉及到的50个Sql语句

一个项目涉及到的50个Sql语句
 
/*
标题：一个项目涉及到的50个Sql语句(整理版)
作者：爱新觉罗.毓华(十八年风雨，守得冰山雪莲花开)
时间：2010-05-10
地点：重庆航天职业学院
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
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
where a.S#  = b.S# and a.S# = c.S# and b.C# =  '01' and c.C# = '02' and b.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
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
where a.S#  = b.S# and a.S# = c.S# and b.C# =  '01' and c.C# = '02' and b.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
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
where a.S#  =
group by
having  cast(avg(b.score)  as decimal(18,2)) >= 60 
order by
 
--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
where a.S#  =
group by
having  cast(avg(b.score)  as decimal(18,2)) < 60 
order by
--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
on a.S#  =
group by
having  isnull(cast(avg(b.score) as decimal(18,2)),0) < 60 
order by
 
--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
where a.S#  =
group by
order by
--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
on a.S#  =
group by
order by
 
--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
where Student.S#  = SC.S# and SC.C#  = Course.C# andCourse.T#  = Teacher.T# and Teacher.Tname  = N'张三'
order by
 
--8、查询没学过"张三"老师授课的同学的信息 
select m.* fromStudent 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
 
--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.* fromStudent , SC whereStudent.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
--方法2
select Student.* fromStudent , SC whereStudent.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
--方法3
select m.* fromStudent 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'
group  by S# having count(1) = 2 
)
order by
 
--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.* fromStudent , SC whereStudent.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
--方法2
select Student.* fromStudent , SC whereStudent.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
 
--11、查询没有学全所有课程的同学的信息 
--11.1、
select Student.*
from
where Student.S#  =
group by Student.S# , Student.Sname , Student.Sage , Student.Ssex having count(C#) < (select  count(C#) from
--11.2
select Student.*
from Student  left join
on Student.S#  =
group by Student.S# , Student.Sname , Student.Sage , Student.Ssex having count(C#) < (select  count(C#) from
 
--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.* fromStudent where S# in
(select  distinct SC.S# fromSC  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.* fromstudent where student.S# not in
(select  distinct sc.S# fromsc , course , teacher  wheresc.C# = course.C#  and course.T# = teacher.T#  and teacher.tname = N'张三')
order by
 
--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
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
 
--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
where student.S#  = SC.S# and sc.score  < 60  andsc.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
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
left join SC b on a.S# =
left join Course c on b.C# =
group by
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 whenN'''+Cname+''' then b.score elsenull end) ['+Cname+']'
from (select distinct Cname from Course) as
set @sql = @sql  + ' , cast(avg(b.score)as decimal(18,2)) '  + N'平均分'  + ' from Student a leftjoin 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
selectm.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) fromSC 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) fromSC 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) fromSC 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) fromSC 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(%)]
fromCourse m , SC n
wherem.C#  =
group by
order by
--方法2
selectm.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) fromSC 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) fromSC 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) fromSC 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) fromSC 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(%)]
fromCourse m 
order by
 
--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
selectt.* , px = (select  count(1)  from SC where C#  = t.C# and score  > t.score) + 1 from sc t order  by
--Score重复时合并名次
selectt.* , px = (select  count(distinct score)  from SC where C#  = t.C# and score  >= t.score) from sc t  order by
--19.2 sql 2005用rank,DENSE_RANK完成
--Score重复时保留名次空缺(rank完成)
selectt.* , px = rank() over(partition by c# order  by score desc) from sc t order by
--Score重复时合并名次(DENSE_RANK完成)
selectt.* , px = DENSE_RANK() over(partition by c# order  by score desc) from sc t order by
 
--20、查询学生的总成绩并进行排名
--20.1 查询学生的总成绩
selectm.S#  [学生编号]
[学生姓名]
isnull(sum(score),0) [总成绩]
fromStudent m  left join SC n on m.S# =
group by
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。
selectt1.* , px = (select  count(1)  from
(
select m.S#  [学生编号]
[学生姓名]
isnull(sum(score),0) [总成绩]
from Student m  left join SC n on m.S# =
group  by
) t2 where 总成绩  > t1.总成绩) + 1 from
(
select m.S#  [学生编号]
[学生姓名]
isnull(sum(score),0) [总成绩]
from Student m  left join SC n on m.S# =
group  by
) t1
order by
 
selectt1.* , px = (select  count(distinct 总成绩)  from
(
select m.S#  [学生编号]
[学生姓名]
isnull(sum(score),0) [总成绩]
from Student m  left join SC n on m.S# =
group  by
) t2 where 总成绩  >= t1.总成绩) from
(
select m.S#  [学生编号]
[学生姓名]
isnull(sum(score),0) [总成绩]
from Student m  left join SC n on m.S# =
group  by
) t1
order by
--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。
selectt.* , px = rank() over(order by [总成绩] desc) from
(
select m.S#  [学生编号]
[学生姓名]
isnull(sum(score),0) [总成绩]
from Student m  left join SC n on m.S# =
group  by
) t
order by
 
selectt.* , px = DENSE_RANK() over(order by [总成绩] desc) from
(
select m.S#  [学生编号]
[学生姓名]
isnull(sum(score),0) [总成绩]
from Student m  left join SC n on m.S# =
group  by
) t
order by
 
--21、查询不同老师所教不同课程平均分从高到低显示 
selectm.T# , m.Tname ,  cast(avg(o.score)  as decimal(18,2)) avg_score
fromTeacher m , Course n , SC o
wherem.T#  = n.T# and n.C# =
group by
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
--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
--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
--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
 
--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
selectCourse.C#  [课程编号] , Cname as [课程名称]
sum(case whenscore >= 85 then 1 else 0 end) [85-100],
sum(case whenscore >= 70 and score < 85 then 1 else 0 end) [70-85],
sum(case whenscore >= 60 and score < 70 then 1 else 0 end) [60-70],
sum(case whenscore < 60 then 1 else 0 end) [0-60]
fromsc , Course 
whereSC.C#  =
group by
order by
--纵向显示1(显示存在的分数段)
selectm.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 
fromCourse m , sc n
wherem.C#  =
group by
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
--纵向显示2(显示存在的分数段，不存在的分数段用0显示)
selectm.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 
fromCourse m , sc n
wherem.C#  =
group by all
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
 
--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
selectm.C# 课程编号, m.Cname 课程名称,
select  count(1)  fromSC where C# = m.C# and score < 60) [0-60],
cast((select count(1) fromSC 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)  fromSC where C# = m.C# and score >= 60 and score < 70) [60-70],
cast((select count(1) fromSC 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)  fromSC where C# = m.C# and score >= 70 and score < 85) [70-85],
cast((select count(1) fromSC 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)  fromSC where C# = m.C# and score >= 85) [85-100],
cast((select count(1) fromSC 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(%)]
fromCourse m 
order by
--纵向显示1(显示存在的分数段)
selectm.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(%)]
fromCourse m , sc n
wherem.C#  =
group by
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
--纵向显示2(显示存在的分数段，不存在的分数段用0显示)
selectm.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(%)]
fromCourse m , sc n
wherem.C#  =
group by all
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
 
--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。
selectt1.* , px = (select  count(1)  from
(
select m.S#  [学生编号]
[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# =
group  by
) t2 where 平均成绩  > t1.平均成绩) + 1 from
(
select m.S#  [学生编号]
[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# =
group  by
) t1
order by
 
selectt1.* , px = (select  count(distinct 平均成绩)  from
(
select m.S#  [学生编号]
[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# =
group  by
) t2 where 平均成绩  >= t1.平均成绩) from
(
select m.S#  [学生编号]
[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# =
group  by
) t1
order by
--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。
selectt.* , px = rank() over(order by [平均成绩] desc) from
(
select m.S#  [学生编号]
[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# =
group  by
) t
order by
 
selectt.* , px = DENSE_RANK() over(order by [平均成绩] desc) from
(
select m.S#  [学生编号]
[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# =
group  by
) t
order by
  
--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
selectm.* , 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
--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
 
--26、查询每门课程被选修的学生数 
selectc# ,  count(S#)[学生数] from sc group  by
 
--27、查询出只有两门课程的全部学生的学号和姓名 
selectStudent.S# , Student.Sname
fromStudent , SC 
whereStudent.S#  =
group by
having  count(SC.C#) = 2
order by
 
--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
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 
selectSname  [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 
selectm.C# , m.Cname ,  cast(avg(n.score)  as decimal(18,2)) avg_score
fromCourse m, SC n 
wherem.C#  =
group by
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 
selecta.S# , a.Sname ,  cast(avg(b.score)  as decimal(18,2)) avg_score
fromStudent a , sc b
wherea.S#  =
group by
having  cast(avg(b.score)  as decimal(18,2)) >= 85 
order by
 
--34、查询课程名称为"数学"，且分数低于60的学生姓名和分数 
selectsname , score
fromStudent , SC , Course 
whereSC.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； 
selectStudent.*
fromStudent, SC , Course 
whereStudent.S#  = SC.S# and SC.C#  =
order by
 
--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； 
selectStudent.*
fromStudent, SC , Course 
whereStudent.S#  = SC.S# and SC.C#  = Course.C# and SC.score  >= 70 
order by
 
--37、查询不及格的课程
selectStudent.*
fromStudent, SC , Course 
whereStudent.S#  = SC.S# and SC.C#  = Course.C# and SC.score  < 60 
order by
 
--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； 
selectStudent.*
fromStudent, SC , Course 
whereStudent.S#  = SC.S# and SC.C#  = Course.C# and SC.C#  = '01' and SC.score >= 80 
order by
 
--39、求每门课程的学生人数 
selectCourse.C# , Course.Cname ,  count(*)[学生人数]
fromCourse , SC 
whereCourse.C#  =
group by
order by
 
--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.*
fromStudent, SC , Course , Teacher
whereStudent.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
selectStudent.*
fromStudent, SC , Course , Teacher
whereStudent.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
selectm.* from SC m ,(select C# , score from SC group  by C# , score having  count(1)  > 1) n 
wherem.C#= n.C# and m.score = n.score order by
--方法2
selectm.* from SC m where  exists (select 1 from (select C# , score from SC group  by C# , score having  count(1)  > 1) n 
wherem.C#= n.C# and m.score = n.score) order by
 
--42、查询每门功成绩最好的前两名 
selectt.* 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  
selectCourse.C# , Course.Cname ,  count(*)[学生人数]
fromCourse , SC 
whereCourse.C#  =
group by
having  count(*) >= 5
order by [学生人数]  desc
 
--44、检索至少选修两门课程的学生学号 
selectstudent.S# , student.Sname 
fromstudent , SC 
wherestudent.S#  =
group by
having  count(1)  >= 2
order by
 
--45、查询选修了全部课程的学生信息 
--方法1 
selectstudent.* from student where S# in
(select S#  from sc group by S# having count(1) = (select  count(1)  from
--方法2 
selectt.* from student t where t.S# not in
(
select  distinct m.S# from
  (
select S# , C#  from
where  not exists(select 1 from sc n where n.S# = m.S# and n.C# =
)
--方法3 
selectt.* from student t where not exists(select 1 from
(
select  distinct m.S# from
  (
select S# , C#  from
where  not exists(select 1 from sc n where n.S# = m.S# and n.C# =
) k where k.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
--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
 
--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