摘要最近張貼的主題與MySQL

Question

我有一個非常基礎的論壇系統。三個主表，主題，評論和用戶都有你想象的所有常見字段，例如自動遞增主鍵和外​​鍵，所以我不認爲我需要詳細說明全部內容

我想要做的是獲得最近發佈的主題列表。列表視圖應顯示主題標題，初始評論/帖子的正文以及作者的姓名，但該列表應與最近最先發布的主題一起排序。

我不是很擅長MySQL以外的最基本的查詢。我顯然可以將它分解成多個查詢，但我希望在一個查詢中獲得性能。

這是我第一次想到的，但它根據第一篇文章的時間排序。

SELECT topic.id as topic_id, topic.title as topic_title, topic.datePosted as datePosted, topic.views as views, topic.numComments as numComments, 
    comment.ID as commentID, comment.body as body, 
user.ID as userID, user.firstName, user.lastName, user.title as user_title, user.city, user.state, user.thumbnail 

FROM comment INNER JOIN topic ON comment.topicID = topic.id 
INNER JOIN user ON comment.userID = user.id 
WHERE comment.id 
     IN (
     SELECT min(comment.id) 
     FROM COMMENT INNER JOIN topic ON comment.topicID = topic.id 
     GROUP BY topic.id 
     ) 

ORDER BY commentID desc'; 

Answer 1

好吧，這是我第一次重擊一下我認爲你要求，每個主題最近發表的評論列表。讓我知道這是不是你在找什麼：

SELECT 
    t.title, 
    t.views, 
    t.numComments, 
    c.id, 
    c.datePosted, 
    c.body, 
    u.firstName, 
    u.lastName 
FROM 
    topic AS t 
    INNER JOIN 
     (SELECT 
      c_inner.topicId, 
      MAX(c_inner.datePosted) AS latestPosted 
     FROM 
      comment AS c_inner 
     GROUP BY 
      c_inner.topicId) AS cmax 
     ON t.id = cmax.topicId 
    INNER JOIN comment AS c 
     ON c.topicId = cmax.topicId AND c.datePosted = cmax.latestPosted 
    INNER JOIN user AS u 
     ON c.userId = u.id 
ORDER BY c.datePosted DESC; 

如果我誤解你在找什麼，你可以發表您想要的結果的例子嗎？