how can i retrieve username from another collection by using join in laravel

//viewing tickets generated by them $user= Auth::user()->_id; $tickets = ticket::where(function ($query) use ($user) { $query->where('user', '=', $user); })->get();

  //  created ticket by which user
    $atickets = ticket::where(function ($query) use ($user) {
        $query->where('user_assigned', '=', $user);
    })->get();


    return view('ticketviews', compact('tickets','atickets'));

$atickets returns record details such as user_id and ticket details, now i need to display the username for that particular record stored in another collection mongodb. Can anyone suggest me the code to do that.

via Chebli Mohamed