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phpmysqlinner-join

Show my posts as well as followers posts in PHP and MySQL


I'm trying to make a homepage somewhat like Facebook, I made it so it could show the posts from the people I follow, but I couldn't see my own posts as I can't follow myself. Here is the line of SQL code I've written (it contains PHP variables):

SELECT * 
FROM user_posts 
INNER JOIN user_following ON user_posts.username = user_following.username 
WHERE user_following.follower = '$me->username' 
ORDER BY id DESC 
LIMIT 0, 15
  1. The user_posts table contains all the posts.
  2. The user_following table contains all follow data, where username is the user being followed, and the follower is the user following the username
  3. $me->username is the username of the user logged in.

user_posts table structure: enter image description here

user_following table structure: enter image description here

Thanks, in advance!


Solution

  • There's a couple of different ways to skin this query:

    Sub-query

    SELECT * 
    FROM user_posts 
    WHERE user_posts.username = 'bob'
    OR user_posts.username IN(
      SELECT username 
      FROM user_following
      WHERE user_posts.username = user_following.username
    )
    LIMIT 0, 15
    

    http://sqlfiddle.com/#!9/6bf2c6/9

    Use the Users Table

    Requires GROUP BY or DISTINCT user_posts.id, which are non-optimal.

    SELECT
       user_posts.* 
    FROM users
    LEFT JOIN user_following ON users.username = user_following.username
    INNER JOIN user_posts ON (
      users.username = user_posts.username
      OR user_following.follower = user_posts.username
    )
    WHERE users.username = 'bob'
    GROUP BY user_posts.id
    LIMIT 0, 15
    

    http://sqlfiddle.com/#!9/d91be/1

    IMPORTANT! Make sure and index those columns in your table. Otherwise, performance will suffer as the tables get bigger (especially user_following).