php - mysql相关领域

Question

这4个字段是相互关联的

我希望它输出为:

在我的查询中:

SELECT users.firstname, users.lastname, users.screenname, posts.post_id, posts.user_id,
posts.post, posts.upload_name, posts.post_type, 
DATE_FORMAT(posts.date_posted, '%M %d, %Y %r') AS date, 
COUNT(NULLIF(feeds.user_id, ?)) AS everybody, SUM(feeds.user_id = ?) AS you,
GROUP_CONCAT(CASE WHEN NOT likes.user_id = ? THEN 
             CONCAT_WS(' ', likes.firstname, likes.lastname)
                    END
            ) as names
FROM website.users users
INNER JOIN website.posts posts ON (users.user_id = posts.user_id)
LEFT  JOIN website.feeds feeds ON (posts.post_id = feeds.post_id)
LEFT  JOIN website.users likes ON (feeds.user_id = likes.user_id)
GROUP BY posts.pid
ORDER BY posts.pid DESC

现在，我有一个问题，我应该加入 friend 表的哪一部分， 我想显示来自friend_id 或user_id 的所有帖子 以及来自当前登录用户的帖子。如果 friend 表 上没有匹配的 friend ，则只输出所有来自用户的帖子。伙计们，我需要你们的帮助。

friends.friend_id = 当前用户的好友

friends.user_id = 用户的当前好友

因此，friends.friend_id = posts.user_id 或 friends.user_id = posts.user_id

如果我的friends表看不懂，请帮我修改一下，让它变得更好。

Answer 1

您想查看来自用户或其 friend 的帖子。因此，不是与用户连接，而是与子查询连接，如下所示:

SELECT users.firstname, users.lastname, users.screenname,
       posts.post_id, posts.user_id, posts.post, posts.upload_name,
       posts.post_type, DATE_FORMAT(posts.date_posted, '%M %d, %Y %r') AS date, 
       COUNT(NULLIF(feeds.user_id, ?)) AS everybody,
       SUM(feeds.user_id = ?) AS you,
       GROUP_CONCAT(CASE WHEN NOT likes.user_id = ? THEN 
             CONCAT_WS(' ', likes.firstname, likes.lastname) END) as names
  FROM (SELECT user_id FROM website.users WHERE user_id = ?
        UNION ALL
        SELECT user_id FROM website.friends WHERE friend_id = ?
        UNION ALL
        SELECT friend_id FROM website.friends WHERE user_id = ?) AS who
  JOIN website.users users ON users.user_id = who.user_id
  JOIN website.posts posts ON users.user_id = posts.user_id
  LEFT  JOIN website.feeds feeds ON posts.post_id = feeds.post_id
  LEFT  JOIN website.users likes ON feeds.user_id = likes.user_i)
 GROUP BY posts.pid
 ORDER BY posts.pid DESC;

测试输出 here .