How can I retrieve specific content from multiple tables in Laravel based on complex relationships, such as building a Twitter-like feed that filters posts based on users a current user follows?

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:

• Share.user_id must be equal to Followers.follower_id
• Followers.user_id must be equal to Users.id

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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