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Laravel Join with Multiple Tables to Filter Content
In this article, we address a common challenge faced when building a social media platform using Laravel: retrieving specific content based on complex relationships between multiple tables. We will provide a comprehensive solution using both raw SQL queries and the Laravel Eloquent ORM.
Problem Statement
The objective is to build a Twitter-like feed that displays posts only from users who the current user follows. To achieve this, we need to filter the "Shares" table based on the following conditions:
SQL Solution
While the original SQL query provided might seem correct, a minor adjustment is required for the join order and the condition to work correctly. The following corrected SQL query effectively joins the three tables and applies the specified filtering:
$shares = DB::table('shares') ->join('users', 'users.id', '=', 'shares.user_id') ->join('followers', 'followers.user_id', '=', 'users.id') ->where('followers.follower_id', '=', 3) ->get();
Alternatively, using the Eloquent ORM offers a more elegant and encapsulated approach. Here's a model-based solution:
User.php (Model)
public function shares() { return $this->hasMany('Share'); } public function followers() { return $this->belongsToMany('User', 'follows', 'user_id', 'follower_id'); } public function followees() { return $this->belongsToMany('User', 'follows', 'follower_id', 'user_id'); }
Share.php (Model)
public function user() { return $this->belongsTo('User'); }
Controller.php (Controller)
$my = User::find('my_id'); $shares = Share::with('user') ->join('follows', 'follows.user_id', '=', 'shares.user_id') ->where('follows.follower_id', '=', $my->id) ->get(); foreach ($shares as $share) { echo $share->user->username; }
This approach provides a more flexible and maintainable solution, ensuring data integrity and efficient queries.
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