学生成绩表（对成绩的操作）

1.计算每个人的总成绩并排名(要求显示字段：姓名，总成绩)

答案：select name,sum(score) as allscore
 from stuscore
 group by name 
order by allscore

2.计算每个人的总成绩并排名(要求显示字段: 学号，姓名，总成绩)

答案：select distinct t1.name,t1.stuid,t2.allscore 

from  stuscore t1,(    select stuid,sum(score) as allscore from stuscore group by stuid)t2 
where t1.stuid=t2.stuidorder by t2.allscore desc

3.计算每个人单科的最高成绩(要求显示字段: 学号，姓名，课程，最高成绩)

答案：select t1.stuid,t1.name,t1.subject,t1.score 
from stuscore t1,(select stuid,max(score) as maxscore from stuscore group by stuid) t2 where t1.stuid=t2.stuid and t1.score=t2.maxscore

4.计算每个人的平均成绩（要求显示字段: 学号，姓名，平均成绩）

答案：select distinct t1.stuid,t1.name,t2.avgscore 
from stuscore t1,(select stuid,avg(score) as avgscore from stuscore group by stuid) t2 
where t1.stuid=t2.stuid

5.列出各门课程成绩最好的学生(要求显示字段: 学号，姓名,科目，成绩)

答案：select  t1.stuid,t1.name,t1.subject,t2.maxscore 
from stuscore t1,(select subject,max(score) as maxscore from stuscore group by subject) t2 where t1.subject=t2.subject and t1.score=t2.maxscore

6.列出各门课程成绩最好的两位学生(要求显示字段: 学号，姓名,科目，成绩)

答案：select distinct t1.* from stuscore t1 where t1.id in (select top 2 stuscore.id from stuscore where subject = t1.subject order by score desc) 
order by t1.subject

7.统计如下：学号     姓名     语文     数学     英语     总分     平均分

答案：select stuid as 学号,name as 姓名,sum(case when subject=’语文’ then score else 0 end) as 语文,sum(case when subject=’数学’ then score else 0 end) as 数学,sum(case when subject=’英语’ then score else 0 end) as 英语,sum(score) as 总分,(sum(score)/count(*)) as 平均分 from stuscoregroup by stuid,name order by 总分desc

8．列出各门课程的平均成绩（要求显示字段：课程，平均成绩）

答案：select subject,avg(score) as avgscore 
from stuscore group by subject

9．列出数学成绩的排名（要求显示字段：学号，姓名，成绩，排名）

答案：

declare @tmp table(pm int,name varchar(50),score int,stuid int)
insert into @tmp select null,name,score,stuid from stuscore where subject=’数学’ order by score desc
declare @id int
set @id=0;
update @tmp set @id=@id+1,pm=@id
select * from @tmp

oracle:
select  DENSE_RANK () OVER(order by score desc) as row,name,subject,score,stuid from stuscore where subject=’数学’order by score desc
ms sql(最佳选择)
select (select count(*) from stuscore t1 where subject =’数学’ and t1.score>t2.score)+1 as row ,stuid,name,score from stuscore t2 where subject =’数学’ order by score desc

10．列出数学成绩在2-3名的学生（要求显示字段：学号，姓名,科目，成绩）

答案：select t3.*  from(select top 2 t2.*  from (select top 3 name,subject,score,stuid from stuscore where subject=’数学’order by score desc) t2 order by t2.score) t3 order by t3.score desc

11．求出李四的数学成绩的排名

答案：

declare @tmp table(pm int,name varchar(50),score int,stuid int)insert into @tmp select null,name,score,stuid from stuscore where subject=’数学’ order by score descdeclare @id intset @id=0;update @tmp set @id=@id+1,pm=@idselect * from @tmp where name=’李四’

12．统计如下：课程     不及格（0-59）个     良（60-80）个     优（81-100）个

答案：select subject, (select count(*) from stuscore where score<60 and subject=t1.subject) as 不及格,(select count(*) from stuscore where score between 60 and 80 and subject=t1.subject) as 良,(select count(*) from stuscore where score >80 and subject=t1.subject) as 优 from stuscore t1 group by subject

13．统计如下：数学:张三(50分),李四(90分),王五(90分),赵六(76分)

答案：

declare @s varchar(1000)set @s=’’select @s =@s+’,’+name+'(’+convert(varchar(10),score)+’分)’ from stuscore where subject=’数学’ set @s=stuff(@s,1,1,’’)print ’数学:’+@s

14.计算科科及格的人的平均成绩

答案： select distinct t1.stuid,t2.avgscore  from stuscore t1,(select stuid,avg(score) as avgscore from stuscore   group by stuid  ) t2,(select stuid from stuscore where score<60 group by stuid) t3 where t1.stuid=t2.stuid and t1.stuid!=t3.stuid;
select  name,avg(score) as avgscore   from stuscore s  where (select sum(case when i.score>=60 then 1 else 0 end) from stuscore i where  i.name= s.name)=3   group by name