获取Laravel中未设置为外键的行的数据

namespace App;

use Illuminate\Database\Eloquent\Model;

class User extends Model
{
    protected $table = 'users';

    public function getNonForeignKeyRows()
    {
        return $this->whereNull('role_id')->get();
    }
}

namespace App\Http\Controllers;

use App\User;
use Illuminate\Http\Request;

class UserController extends Controller
{
    public function index()
    {
        $users = User::getNonForeignKeyRows();

        // 处理获取到的数据
        // ...

        return view('users.index', compact('users'));
    }
}