2011-08-15

MySQL获取所有分类和每个分类的前N条记录

2+

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,转自(loveyuki.com),感谢。

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。

本文有 2 篇评论 ↓↓

  1. 之前都没有用过HAVING还不知道什么意思,刚好学习一下

  2. 好高深的SQL