WTO對與GROUP BY表和ORDER BY MAX（）

Question

此代碼正常工作

SELECT 
    c.id_article, 
    a.titre AS title_article 
FROM comments AS c 
LEFT JOIN articles AS a 
    ON a.id = c.id_article 
WHERE c.hide = 0 
GROUP BY c.id_article 
ORDER BY MAX(c.date) DESC 
LIMIT 0, 6 

但我需要在最後文章評論的用戶名。

我試試這個

SELECT 
    c.id_article, 
    a.titre AS title_article, 
    u.nom_utilisateur AS user_name 
FROM comments AS c 
LEFT JOIN articles AS a 
    ON a.id = c.id_article 
LEFT JOIN membres AS u 
    ON c.id_user = u.id 
WHERE c.hide = 0 
GROUP BY c.id_article 
ORDER BY MAX(c.date) DESC 
LIMIT 0, 6 

和不工作...

任何幫助嗎？

（對不起我的英文不好...）

Answer 1

沒有錯誤消息或說明什麼是錯了，它是一種很難說，但在任何情況下，你沒有包括在GROUP BY聲明u.nom_utilisateur 。

MySQL通常允許這個沒有拋出錯誤，但它可能會導致意想不到的結果。

SELECT 
    c.id_article, 
    a.titre AS title_article, 
    u.nom_utilisateur AS user_name 
FROM comments AS c 
LEFT JOIN articles AS a 
    ON a.id = c.id_article 
LEFT JOIN membres AS u 
    ON c.id_user = u.id 
WHERE c.hide = 0 
GROUP BY c.id_article, u.nom_utilisateur 
ORDER BY MAX(c.date) DESC 
LIMIT 0, 6 

Answer 2

我有一個部分的解決方案。

我使用此代碼從文章檢索最後意見：

SELECT 
    c.id_article, 
    MAX(c.id) AS last_id_comment, 
    a.titre AS title_article 
FROM comments AS c 
LEFT JOIN articles AS a 
    ON a.id = c.id_article 
WHERE c.hide = 0 
GROUP BY c.id_article 
ORDER BY MAX(c.date) DESC 
LIMIT 0, 6 

和之後而第一選擇，我使用此代碼爲檢索來自最後的評論用戶名：

SELECT 
    u.nom_utilisateur AS username 
FROM comments AS c 
LEFT JOIN membres AS u 
    ON u.id = c.id_user 
WHERE c.id = :last_id_comment 

不是最好的解決方案，但它的工作。