MySQL每一個分類的前幾條記錄

MySQL 獲取全部分類和每一個分類的前幾條記錄

好比有文章表 Article(Id,Category,InsertDate)

如今要用SQL找出每種類型中時間最新的前N個數據組成的集合

 

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 就是要取多少條