How to make a selection of goods by sections in bitrix?

Question

MySQL

Hello!
how to make a selection of goods from sections, for example, there are sections:
Household appliances
-- Refrigerators
-- -- Built-in (6 pcs)
-- -- Stand- alone (8 pcs)
the product has a link to the final category, and already the categories have a link to the parent
as on pure sql to make a query to display the number of products in categories? that is, the result should be like this:
Household appliances - 14pcs
Refrigerators - 14pcs Built
-in 6pcs Stand-alone 8pcs It is not clear how to make a selection for parent categories where there is no direct connection with the product.

Answer 1

The easiest way is to select all product-section links and calculate in php