比如有文章表 Article(Id,Category,InsertDate)，现在要用SQL找出每种类型中时间最新的前N个数据组成的集合，一段不错的代码，留存备用

SELECT A1.*

FROM Article AS A1

INNER JOIN (SELECT A.Category,A.InsertDate

FROM Article AS A

LEFT JOIN Article AS B

ON A.Category = B.Category

AND A.InsertDate <= B.InsertDate

GROUP BY A.Category,A.InsertDate

HAVING COUNT(B.InsertDate) <= @N

) AS B1

ON A1.Category = B1.Category

AND A1.InsertDate = B1.InsertDate

ORDER BY A1.Category,A1.InsertDate DESC

@N 就是你要取多少条

下面是我用到了一个产品分类表中，superId是大分类，prcid是产品分类。能用SQL完成的功能就要尽量用SQL语句来完成，这既简洁又高效。

SELECT

A1.*

FROM

prcKx AS A1

INNER JOIN (

SELECT

A.superId,

A.prcid

FROM

prcKx AS A

LEFT JOIN prcKx AS B ON A.superId = B.superId

AND A.prcid <= B.prcid

GROUP BY

A.superId,

A.prcid

HAVING

COUNT(B.prcid) <= 7

) AS B1 ON A1.superId = B1.superId

AND A1.prcid = B1.prcid

ORDER BY

superId,

prcid

需求是这样的(CSDN上的一个问题)：mysql中有个表：article(字段：id,type,date)，type有1-10，10种类型。现在要用SQL找出每种类型中时间最新的前N个数据组成的集合。

这个问题应该有很多方法可以实现，下面就来说说在网上看到的一位高手的实现(用一条SQL语句实现的，个人感觉非常好，所以拿来和大家分享)：

select a1.* from article a1

inner join

(select a.type,a.date from article a left join article b

on a.type=b.type and a.date<=b.date

group by a.type,a.date

having count(b.date)<=2

)b1

on a1.type=b1.type and a1.date=b1.date

order by a1.type,a1.date desc

注：上面sql语句中的2代表的就是前面提到的N。

以上所述就是本文的全部内容了，希望大家能够喜欢。