Question

一些背景知识：

我正在开发一种社交网络。有下表的DB：

users(user_id, user_name, password, etc.)
posts(post_id, user_id, post_text, post_data, etc.)
followings(relationship_id, follower_id, following_id, added_date_time)
likes(like_id, user_id, post_id, added_date_time)
comments(comment_id, user_id, post_id, comment_text, added_date_time)

问题是：

我如何实现查询，该查询将获取有关我的以下（我关注的人）最近做过的事情的信息（例如有人喜欢/评论某事）并通过date_time订购此信息数组？

我可以使用一个查询制作吗？或者我必须自己做多个查询并用PHP处理所有这些东西？

最好的方法是什么？

Answer 1

您必须至少分离对喜欢和评论的查询，因为结果集不同。

否则您的查询将会显示为像：

SELECT comment_id,comment_text,added_date_time FROM comments WHERE user_id IN (SELECT following_id FROM followings WHERE follower_id={{USER_ID_FROM_USER}}) ORDER BY added_date_time

这将为您提供按日期排序的{{USER_ID_FROM_USER}}后面的人的评论。

Answer 2

您可以在这样的选择联合中规范化输出

SELECT t.type, t.user_id, u.user_name, t.type_id, t.post_id, t.text, t.added_date_time 
  FROM (
  SELECT 'posts' as type, p.user_id, p.post_id as type_id, p.post_id, post_text as text, p.added_date_time
    FROM posts p  
    JOIN followings f ON (f.following_id = p.user_id) 
   WHERE f.follower_id = @user
   UNION
  SELECT 'comments' as type, c.user_id, c.comment_id as type_id, c.post_id, comment_text as text, c.added_date_time
    FROM comments c
    JOIN followings f ON (f.following.id = c.user_id)
   WHERE f.follower_id = @user
   UNION
  SELECT 'likes' as type, l.user_id, l.like_id as type_id, l.post_id, post_text as text, l.added_date_time
    FROM likes l
    JOIN followings f ON (f.following.id = c.user_id)
    JOIN posts p ON (l.post_id = p.post_id)
   WHERE f.follower_id = @user
  ) as t 
JOIN users u ON (t.user_id = u.user_id) 
ORDER BY added_date_time DESC;

因此，您只能在一个查询中获取所有数据。

我希望它适合你。

您关注的人的mysql活动供稿（喜欢，评论等）

2 个答案: