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

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

?

ps: ?@N 就是要取多少条