Aggregating Relations

[tonytoth]

Hello guys,
Im wondering if I can achieve this using aggregates.
e.g: I have a tree of relations: product -> resource -> boughtResource (userId, resourceId).

I want to be able to tell that for product 7, the current user has bought 20 different resources (based on boughtResource).
Im not sure if I can achieve this by using aggregates or I have to do something custom for it.
I tried to use aggregates but don't think I can achieve this as from what I've seen, you can only do sum of fields, not of relations.

Hopefully it makes sense.
Thank you,
Tony

[tonytoth]

Actually I managed to solve this by using filters.