Question

我正在尝试按照userID（查询中的?）后面的用户获取帖子，并由?用户自己获取帖子。

SELECT 
    posts.id AS postid, posts.user AS user, posts.images AS images, posts.post_created, posts.textvalue, posts.textpost,
    users.username AS authorname
FROM posts
INNER JOIN follows ON (posts.user = follows.follows AND follows.user = ?) OR posts.user = ?
INNER JOIN users ON users.id = posts.user
ORDER BY posts.post_created DESC LIMIT 20

此查询有效，但是对于?的每个帖子，它都会返回该行两次，当我删除OR posts.user = ?时，它可以正常工作，但不会显示?的帖子用户身份。

Answer 1

我相信你想要

SELECT p.*, u.username AS authorname
FROM posts p INNER JOIN
     users u
     ON u.id = p.user LEFT JOIN
     follows f
     ON p.user = f.follows AND f.user = ?
WHERE f.user IS NOT NULL OR  -- a match on the "follows" condition
      p.user = ?             -- a match on the post condition   
ORDER BY p.post_created DESC
LIMIT 20;

您的查询是一个令人困惑的问题。但基本上，您对于来自用户的帖子具有以下条件：

FROM posts p INNER JOIN
     follows f
     ON p.user = ?

（忘记OR部分-只会进一步增加行数。）

两个表之间没有JOIN条件，因此在该帖子后面的每个用户都会得到一行。

具有内部联接的MySQL查询返回重复的结果

1 个答案: