DB queries the database, merges two unrelated tables, adds non-existent fields, and assigns default values

demand ： There are two unrelated tables in the two databases , I need to merge them , And in order2 Add nonexistent product_name Field , And give default values

 $product_name = ' The default value is ';
 $news = DB::table("guild_pay.order1")
 		->where('status', '=', 1)
     	->selectRaw('product_name','order_no','money','create_time');
 $res = Db::table('guild_pay.order2')
       	->where('status', '=', 1)
 		->union($news)
     	->selectRaw('IFNULL(null, ?) as product_name, order_no, money, create_time', [$product_name])
     	->orderBy('create_time', 'desc')
     	->paginate(10)->toArray();

ps： Remember that the fields of the two tables should correspond to each other , You can't have more at the same time and less at the same time , You can't change the position