共享一SQL面试题

dandan

有一个表LEANR，表里有三个字段分别是学生ID（student_id），课程（kc）,成绩（grade），要求用一条查询语句搜索出每一门课程的前两名。
答案：select student_id,kc,grade from (select student_id,kc,grade,number=(select count(distinct grade) from learn where t.kc=kc and t.grade<grade) from learn t ) tt where number>2

[ 本帖最后由 dandan 于 2007-4-12 12:18 编辑 ]

wangvivian

谢谢机楼主..

irya@163.com

thanks very much

songliu8410

实在太好了

anTidd

不知道我的对不，很久没写SQL了
select top 2 *
from (select * from learn order by grade desc)
where kc in (select distinct (kc) from learn)

anTidd

select top 2 *
from (select * from learn order by kc, grade desc) a
where a.kc in (select distinct (kc) from learn)

bleu

楼主的SQL错了

select  student_id, kc,grade from (
select  student_id,kc,grade,row_number over (partition by kc order by grade desc) rn from  leanr
) where  rn<=2

aqwdao

很不错

zhjjtmcn

谁的语句是对的

wei_jc

3Q

Helen_px

select b.student_id,b.kc,grade,b.number
from (select student_id,kc,grade,number=(select count(*) from leanr where  kc=t.kc and grade>=t.grade )
      from leanr t) b
where b.number<=2
order by b.kc,b.grade desc,b.number

[ 本帖最后由 Helen_px 于 2007-11-7 11:32 编辑 ]

yuxuan555269

我感觉6楼的对的

软件测试论坛

我建过表验证过了，#11是对的。

williamcool

学习下

李玮123456

如果考虑到一样的分数，楼上的sql应该修改下
select b.id,b.kc,grade,b.number
from (select id,kc,grade,number=(select count(*) from learn where  kc=t.kc and grade>t.grade )
      from learn t) b
where b.number<=1
order by b.kc,b.grade desc,b.number

kfc427

楼主给的语句在postgresql 试了一下。

ERROR: column "num" does not exist

kfc427

在 postgresql 试了一下

select course,student,grade,row_id from
(select *,row_number() over (partition by course order by grade desc) as row_id from learn) as l where row_id<3 order by course

可以完美解决相同分数的问题