how can I send one query result (via variable) into an other query - development

how can I send one query result (via variable) into an other query

What I want is to include the result of sub variable into another query.

 $sub = DB::table('chef_food_ethics')->
 select(DB::raw('count(id) as fCount'))
 ->where('chef_food_ethics.food_ethic_id',
 '=','food_ethic_managers.food_ethic_id')
 ->toSql();

Is it possible to include it like that?

 $r = DB::table('food_ethic_managers')where
 ('food_ethic_managers.manager_id','=',$id)
 ->leftJoin('staff','food_ethic_managers.food_ethic_id'
  ,'=','staff.id')
 ->leftJoin('regions','staff.region_id','=','regions.id')
 ->with($sub)
 ->get();

from Laravel Questions and Answers https://laravelquestions.com/laravel/how-can-i-send-one-query-result-via-variable-into-an-other-query/
via Lzo Media