共享一SQL面试题

dandan 发表于 2007-4-12 11:49:49

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 发表于 2007-4-18 16:13:26

谢谢机楼主..

irya@163.com 发表于 2007-4-25 13:55:54

thanks

thanks very much

songliu8410 发表于 2007-9-20 19:37:29

实在太好了

anTidd 发表于 2007-9-30 22:38:15

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 发表于 2007-9-30 22:44:22

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

bleu 发表于 2007-10-11 09:54:17

楼主的SQL错了

selectstudent_id, kc,grade from (
selectstudent_id,kc,grade,row_number over (partition by kc order by grade desc) rn fromleanr
) wherern<=2

aqwdao 发表于 2007-10-19 08:54:25

很不错

zhjjtmcn 发表于 2007-10-28 01:49:11

谁的语句是对的

wei_jc 发表于 2007-11-1 13:05:52

Helen_px 发表于 2007-11-7 11:02:44

select b.student_id,b.kc,grade,b.number
from (select student_id,kc,grade,number=(select count(*) from leanr wherekc=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 发表于 2007-11-21 15:02:07

我感觉6楼的对的

软件测试论坛 发表于 2008-3-18 14:08:27

我建过表验证过了，#11是对的。

williamcool 发表于 2008-3-19 14:27:00

回复 13# 的帖子

学习下:)

李玮123456 发表于 2016-11-21 14:59:53

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 wherekc=t.kc and grade>t.grade )
from learn t) b
where b.number<=1
order by b.kc,b.grade desc,b.number

kfc427 发表于 2016-11-30 15:37:36

楼主给的语句在postgresql 试了一下。

ERROR: column "num" does not exist

kfc427 发表于 2016-11-30 16:36:45

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

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