DB structure for individual file permissions

A better approach would be to use a pivot table to store the many-to-many relationship between users and files. You can create a pivot table called file_user with columns file_id and user_id. This table would store a row for each user that has been granted permission to view a file.

Here's an example of how you could set up the pivot table and model relationships in your Laravel application:

// File model
class File extends Model
{
    public function users()
    {
        return $this->belongsToMany(User::class, 'file_user');
    }
}

// User model
class User extends Authenticatable
{
    public function files()
    {
        return $this->belongsToMany(File::class, 'file_user');
    }
}

With this setup, you can easily query the pivot table to determine which users have permission to view a given file. For example, to get all users that have permission to view a file with ID 1:

$file = File::find(1);
$users = $file->users;

Alternatively, you can also query the pivot table directly:

$users = User::whereHas('files', function($query) {
    $query->where('file_id', 1);
})->get();