Question

我有2个表：猫（类别）和帖子。
我想按每个类别选择发布。

我试过这个：

SELECT * FROM cat
RIGHT JOIN (SELECT * FROM post WHERE post.CatID=cat.ID LIMIT 3 ) ...

问题是MySQL无法识别子查询中的cat.ID。

此致

Answer 1

SELECT  a.ID, 
        a.Category,
        b.Description
FROM    Category a
        INNER JOIN Post b
            ON a.ID = b.Cat_ID
WHERE   
(
    SELECT  COUNT(*)
    FROM    Post c
    WHERE   b.Cat_ID = c.Cat_ID AND
            b.ID <= c.ID
) <= 2

SQLFiddle Demo

SELECT n row FROM table1 PER table2

1 个答案: