日期:2014-05-18  浏览次数:20455 次

求一个查询语句,今天的一道面试题!
表T1 字段StudentID,StudentName;
表T2 字段StudentID,CourseID,Score;
表T3 字段CourseID , CourseName
查询出每门课成绩都大于课程平均分的同学的名字和课程名


------解决方案--------------------
select studentid from T2 A,
(select CourseID,avg(Score) Score from T2 group by CourseID) B
where A.CourseID = B.CourseID and A.Score > B.Score
group by studentid having count(*) = (select count(*) from T3)

------解决方案--------------------
SQL code

select T1.StudentName, T3.CourseName
from T1
JOIN T2 ON T1.StudentID = T2.StudentID
JOIN T3 ON T2.CourseID = T3.CourseID
where T1.StudentID in
(    select StudentID 
    from T1
    Where NOT Exists (Select score from T2 tt where StudentID = T1.StudentID And score <= (Select Avg(score)from T2 where courseID = tt.courseID))
)

------解决方案--------------------
select T.StudentName , T3.CourseName from
(
select C.StudentName from T2 A, T1 C,
(select CourseID,avg(Score) Score from T2 group by CourseID) B
where A.CourseID = B.CourseID and A.Score > B.Score and C.StudentID = A.StudentID
group by StudentName having count(*) = (select count(*) from T3)
) T
CROSS JOIN T3
------解决方案--------------------
select t1.StudentName,t3.CourseName from t2 left join t1 on t2.StudentID=t1.StudentID
left join t3 on t2.CourseID=t3.CourseID where t2.studentid 
in 
(
select StudentID
from
(select courseid,avg(score) as score from t2 group by courseid) t,
t2 
where 
t2.CourseID=t.CourseID 
and t2.score>t.score 
group by StudentID
having count(t2.CourseID)=(select count(*) from t3)
)

------解决方案--------------------
/*测试环境*/

create table t1 
(
StudentID int,
StudentName varchar(100)
)
create table t2
(
StudentID int,
CourseID int,
Score int
)
create table t3
(
CourseID int,
CourseName varchar(100) 
)

insert t1 select 1,'zhang san'
union all 
select 2,'li si'
union all
select 3,'wang wu'

truncate table t2
insert t2 select 1,1,20
union all
select 1,2,40
union all 
select 2,1,50
union all 
select 2,2,80
union all
select 3,1,30
union all
select 3,2,80

insert t3 select 1,'shuxue'
union all
select 2,'yuwen'


/*sql语句*/
select t1.StudentName,t3.CourseName 
from t2 
left join t1 on t2.StudentID=t1.StudentID
left join t3 on t2.CourseID=t3.CourseID 
where t2.studentid 
in 
(
select StudentID
from
(select courseid,avg(score) as score from t2 group by courseid) t,
t2 
where 
t2.CourseID=t.CourseID 
and t2.score>t.score 
group by StudentID
having count(t2.CourseID)=(select count(*) from t3)
)


/*结果*/
li si shuxue
li si yuwen

------解决方案--------------------
SQL code

Select A.StudentName,C.CourseName 
From 表T1 As A,表T2 As B,表T3 As C,(Select CourseID,Avg(Score) As Score From 表T2 Group By CourseID) As D
Where A.StudentID=B.StudentID And B.CourseID=C.CourseID And B.CourseID=D.CourseID And B.Score>D.Score

------解决方案--------------------
理解错了????
LZ,只显示姓名就可以了吧,为什么把课程也要显示出来!Try
SQL code

Select 
      Distinct A.StudentName
From 
      表T1 As A,
      表T2 As B,
     (Select CourseID,Avg(Score) As Score From 表T2 Group By CourseID) As C,
     (Select StudentID,Count(1) As Counts From 表T2 Group By Studen