为什么操作员LIMIT不能正常工作？

Question

我写了一个查询SQL用于获取与再评论最后意见：

SELECT c.*, ar.ArticleName, ar.idArticle, du.DetailToUsersName, du.DetailToUsersPhoto, COUNT(c.idCommentToArticle) AS CNT, CASE WHEN d.Count IS NULL THEN 0 ELSE d.Count END AS CountLikes 
FROM commenttoarticle c 

INNER JOIN (SELECT CommentToArticlePID FROM commenttoarticle 
GROUP BY CommentToArticlePID 
ORDER BY CommentToArticlePID LIMIT 3) AS articleComments 
USING (CommentToArticlePID) 

LEFT JOIN article ar ON c.CommentToArticleIdArticle = ar.idArticle 
LEFT JOIN detailtousers du ON du.idDetailToUsers = c.CommentToArticleIdUser 
LEFT JOIN `likes` d ON (d.IdNote = c.idCommentToArticle AND d.LikeType = 6) 

WHERE c.CommentToArticleIdArticle = 11 
GROUP BY c.idCommentToArticle 

那么，为什么运营商LIMIT 3子查询中选择不工作？现在，这个查询显示，从表中的所有行commenttoarticle

我似乎需要做的somethink像为：

SELECT... 
FROM (select * from commenttoarticle commenttoarticle c INNER JOIN 
      (SELECT distinct(CommentToArticlePID) 
       FROM commenttoarticle b 
       ORDER BY CommentToArticlePID 
        LIMIT 2) AS commenttoarticle USING (CommentToArticlePID)) as c 

      LEFT JOIN article ar ON c.CommentToArticleIdArticle = ar.idArticle... 

转储表commenttoarticle：

CREATE TABLE IF NOT EXISTS `commenttoarticle` (
    `idCommentToArticle` int(11) NOT NULL AUTO_INCREMENT, 
    `CommentToArticleTime` int(11) NOT NULL, 
    `CommentToArticleIdArticle` int(11) NOT NULL, 
    `CommentToArticleComment` text NOT NULL, 
    `CommentToArticleIdUser` int(11) NOT NULL, 
    `CommentToArticlePID` int(11) NOT NULL, 
    PRIMARY KEY (`idCommentToArticle`), 
    UNIQUE KEY `idCommentToArticle_UNIQUE` (`idCommentToArticle`) 
) ENGINE=MyISAM DEFAULT CHARSET=utf8 AUTO_INCREMENT=59 ; 


INSERT INTO `commenttoarticle` (`idCommentToArticle`, `CommentToArticleTime`, `CommentToArticleIdArticle`, `CommentToArticleComment`, `CommentToArticleIdUser`, `CommentToArticlePID`) VALUES 
(29, 0, 11, 'продажам?\nИнтересует не мега-звезда, а именно предметный, руками умеющий продавать сам и помогающий выстраивать это бизнесам.', 459, 0), 
(30, 0, 11, '2', 459, 0), 
(31, 0, 11, '3', 459, 0), 
(36, 0, 11, '3.1', 459, 31), 
(37, 1413822798, 11, 'also facing that prob. on the plteform of win 7', 459, 29), 
(38, 0, 11, ' here i dont have internet connection.. @Samint Sinha thanks ill check it out maybe tomorrow.', 459, 29), 
(39, 0, 11, ' Select max id and you will have dhe last row returned', 459, 29), 
(32, 0, 11, '4', 459, 0), 
(44, 1414354324, 11, 'How to do', 456, 29), 
(45, 1414354469, 11, 'sfsfsf', 456, 29), 
(46, 1414354708, 11, 'dddd', 456, 29), 
(47, 1414357761, 11, 'sfsfs', 456, 0), 
(57, 1414370833, 39, 'kkkppppppp', 456, 0), 
(49, 1414358233, 11, 'VSF\nSFSF', 456, 0), 
(50, 1414359589, 11, 'How to do', 456, 0), 
(51, 1414359660, 11, 'sfsfsdf', 456, 0), 
(52, 1414361057, 11, 'SDFSF', 456, 0), 
(53, 1414364023, 11, 'dsfdsjfsifmsi', 456, 0), 
(54, 1414364031, 11, 'sdfdskjfnskf', 456, 52), 
(55, 1414364034, 11, 'sdfdskjfnskf', 456, 52), 
(56, 1414364044, 11, 'fndsdfnsofosfi', 456, 52), 
(58, 1414370841, 39, 'dfgdfgdgdgdgdgdfgdgdfg', 456, 0); 

转储表的文章：

CREATE TABLE IF NOT EXISTS `article` (
    `idArticle` int(11) NOT NULL AUTO_INCREMENT, 
    `ArticleName` varchar(255) NOT NULL, 
    `ArticleTime` int(11) NOT NULL, 
    `ArticleDescription` varchar(500) NOT NULL, 
    `ArticleText` text NOT NULL, 
    `ArticleToUserID` int(11) DEFAULT NULL, 
    `ArticleCategory` int(11) NOT NULL, 
    `ArticleView` int(11) NOT NULL, 
    `ArticleCountry` int(11) NOT NULL, 
    `ArticlePhoto` varchar(150) NOT NULL, 
    `ArticleCity` int(11) NOT NULL, 
    PRIMARY KEY (`idArticle`), 
    UNIQUE KEY `idArticle_UNIQUE` (`idArticle`) 
) ENGINE=MyISAM DEFAULT CHARSET=utf8 AUTO_INCREMENT=50 ; 

Answer 1

通过构建自连接上的评论yuo're没有限制，但繁殖的结果。 你需要的是在意见表

SELECT c.*, ar.ArticleName, 
    ar.idArticle, du.DetailToUsersName, 
    du.DetailToUsersPhoto, COALECSE(SUM(d.count), 0) 
FROM 
    (SELECT * 
    FROM 
     commenttoarticle 
    WHERE 
     CommentToArticleIdArticle = 11 
    ORDER BY 
     CommentToArticlePID, idCommentToArticle DESC 
    LIMIT 3 
    ) c 
LEFT JOIN 
    article ar 
    ON c.CommentToArticleIdArticle = ar.idArticle 
LEFT JOIN 
    detailtousers du 
    ON du.idDetailToUsers = c.CommentToArticleIdUser 
LEFT JOIN 
    likes d 
    ON (d.IdNote = c.idCommentToArticle AND d.LikeType = 6) 
GROUP BY 
    c.idCommentToArticle 

我所做的假设，即评论可以在喜欢表中多个条目的单一子查询，否则子查询和不necesarry组。

Answer 2

The USING(column_list) clause names a list of columns that must exist in both tables. 

参考：http://dev.mysql.com/doc/refman/5.0/en/join.html

CommentToArticlePID是不是在你的第一个表。

此外，什么是加入一个单列的点？是的，如果你想限制，这可能适用，但为什么我们LIMIT？