(select 100 * ((SUM(time_product)/SUM(rt_id_count))*SUM(rental_cost))/SUM(sale_count)  FROM

  (select p2.id, p2.inventory_type, p2.working_value, COUNT(distinct p2.id),

  ----nested values calculated here
   (case p2.inventory_type
      when 'set' then
      [calculation A]
    else [calculation B] end) rental_cost,
    (case p2.inventory_type
      when 'set' then
      [caluculation A]
    else [calculation B]  end)   sale_count,
    (case p2.inventory_type
      when 'set' then count(distinct rt.id)
      else 1 end
      ) rt_id_count,
    (case p2.inventory_type
      when 'set' then
      [calculation ]  end)   time_total,
 [calculation]  time_product

  FROM warehouses w
    LEFT JOIN rfid_tags rt ON w.id = rt.location_id AND rt.location_type = 'Warehouse'
    LEFT JOIN products p2 ON rt.ancestor_product_id = p2.id
    LEFT JOIN category_assignments ca  ON ca.product_id = p2.id
    LEFT JOIN categories c ON ca.category_id = c.id
    LEFT JOIN product_selections ps ON ps.rfid_tag_id = rt.id

    WHERE
      c.id=categories.id AND ca.primary = true  AND w.id=warehouses.id
      AND (select count(ps.id) from product_selections ps where ps.rfid_tag_id=rt.id)>0
      and p2.working_value>0
    AND rt.location_id=w.id
    group by p2.id, p2.inventory_type, p2.working_value, c.sale_price_percentage, c.rental_price_percentage) Z) roi