laravel elocuente donde no es igual a
Code::where('to_be_used_by_user_id', '!=' , 2)->orWhereNull('to_be_used_by_user_id')->get()
D3signa
Code::where('to_be_used_by_user_id', '!=' , 2)->orWhereNull('to_be_used_by_user_id')->get()