MySQL查詢以獲取每個類別中的最后一條記錄

Question

我有兩個表： 文章和類別 （大約20個類別），我想得到最新的10篇文章，但不超過一個類別。

表文章

id | title | text

表類別

id | name

表ArticlesCategories （文章和類別之間的關系表）

article | category

我使用下面的查詢，但問題是10結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

將ORDER BY id DESC添加到您的查詢中

這是獲取最后10行的方法是顛倒順序並選擇前十行​​：

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