MySQL查询以获取每个类别中的最后一条记录

Question

我有两个表： 文章和类别 （大约20个类别），我想得到最新的10篇文章，但不超过一个类别。

表文章

id | title | text

表类别

id | name

表ArticlesCategories （文章和类别之间的关系表）

article | category

我使用下面的查询，但问题是10结果不是所有最新的文章。

SELECT id, title, categoryId, categoryName
FROM ( 
        SELECT a.id, a.title, ac.category AS categoryId, c.name AS categoryName
        FROM articles AS a 
            LEFT JOIN articles_categories AS ac ON ac.article = a.id 
            LEFT JOIN categories AS c ON c.id = ac.category 
        WHERE ac.priority = 1 
        ORDER BY a.id DESC ) AS tmp_table 
GROUP BY categoryId LIMIT 10

Answer 1

将ORDER BY id DESC添加到您的查询中

这是获取最后10行的方法是颠倒顺序并选择前十行​​：

SELECT id, title, categoryId, categoryName
FROM ( 
        SELECT a.id, a.title, ac.category AS categoryId, c.name AS categoryName
        FROM articles AS a 
            LEFT JOIN articles_categories AS ac ON ac.article = a.id 
            LEFT JOIN categories AS c ON c.id = ac.category 
        WHERE ac.priority = 1 
        ORDER BY a.id DESC ) AS tmp_table 
GROUP BY categoryId  ORDER BY id DESC LIMIT 10