MySQL的相關領域

Question

這4個領域是相互關聯的

我希望它輸出爲：

在我查詢：

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 

現在，我遇到問題，我應該加入朋友表, 我想顯示來自friend_id或user_id的所有帖子以及當前登錄的用戶的帖子。如果沒有朋友匹配好友表，那麼只輸出用戶的所有帖子。請大家，我需要你的幫助。

friends.friend_id =朋友當前用戶的

用戶的

friends.user_id =當前朋友

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

如果我的朋友表不可理解，請幫我改變它以使其更好。

Answer 1

你想看到的帖子來自用戶，或從他的朋友。因此，而不是與用戶的加盟，攜手同子查詢，像這樣：

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; 

測試輸出here。

Answer 2

如果我很清楚你要根據朋友= USER_ID加入朋友表，如果不匹配JOIN在朋友表user_ID的，所以你可以用這樣的嘗試：

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 friends, 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) 
LEFT JOIN website.friends friends ON ((posts.user_id = friends.user_id) OR (posts.user_id = friends.friends_id)) 
GROUP BY posts.pid 
ORDER BY posts.pid DESC 

我基本上添加了一個加入朋友表與OR或在你似乎想加入的兩個領域...