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。