MySQL Select/Join 仅返回第一行答案

【问题标题】：MySQL Select/Join returning only first rowMySQL Select/Join 仅返回第一行
【发布时间】：2012-07-27 23:05:47
【问题描述】：

我有这个MySQL 查询要从我的数据库中返回一些数据，但由于某种原因，它只返回第一行，我做错了什么？

SELECT `a`.`id` AS topic_id, `a`.`text` AS topic_text, 
 `a`.`date` AS topic_date, `b`.`name` AS author_name, 
 `b`.`picture` AS author_picture, `b`.`facebook_id` AS author_facebook_id, 
SUM(CASE WHEN c.topic_id IS NOT NULL THEN 1 ELSE 0 END) AS topic_likes_number, 
SUM(CASE WHEN c.topic_id IS NOT NULL AND c.author_id = 1 THEN 1 ELSE 0 END) AS topic_liked, 
SUM(CASE WHEN d.topic_id IS NOT NULL THEN 1 ELSE 0 END) AS topic_dislikes_number, 
SUM(CASE WHEN d.topic_id IS NOT NULL AND c.author_id = 1 THEN 1 ELSE 0 END) AS topic_disliked, 
SUM(CASE WHEN e.topic_id IS NOT NULL THEN 1 ELSE 0 END) AS topic_comments_number
    FROM (`topics` AS a)
    INNER JOIN `users` AS b ON `b`.`id` = `a`.`author_id`
    LEFT JOIN `topics_likes` AS c ON `c`.`topic_id` = `a`.`id`
    LEFT JOIN `topics_dislikes` AS d ON `c`.`topic_id` = `a`.`id`
    LEFT JOIN `comments` AS e ON `e`.`topic_id` = `a`.`id`
    LIMIT 50

这是我所期待的（多个主题）：

这就是我得到的（一个主题）：

Array
(
    [0] => Array
        (
            [topic_id] => 1
            [topic_text] => Donec id elit non mi porta gravida at eget metus. Fusce dapibus, tellus ac cursus commodo, tortor mauris condimentum nibh, ut fermentum massa justo sit amet risus. Etiam porta sem malesuada magna mollis euismod. Donec sed odio dui.
            [topic_date] => 0000-00-00 00:00:00
            [author_name] => Claudius Ibn
            [author_picture] => 356a192b7913b04c54574d18c28d46e6395428ab.jpg
            [author_facebook_id] => 100003268692398
            [topic_likes_number] => 1
            [topic_liked] => 1
            [topic_dislikes_number] => 0
            [topic_disliked] => 0
            [topic_comments_number] => 0
        )

)

解决方案： 只需添加一个 group_by a.id

【问题讨论】：

您能否向我们展示一些您的数据示例、所需数据以及您获得的输出？
我期待一个包含多个数组（主题）的数组，但我得到一个只有一个数组（主题）的数组。
再次向我们展示一些输出。如果我们看不到您的数据，我们就不是巫师

标签： mysql select join left-join

【解决方案1】：

这行似乎是错误的，即使它可能不是你的问题：

LEFT JOIN `topics_dislikes` AS d ON `c`.`topic_id` = `a`.`id`

【讨论】：