Alright, I have a table that looks like:

order_id | prod_id | prod_ppu | quantity
It's an associative entity. What I need to select is the top 6 sellers (so the products with the highest quantity bought) and display them. The problem I am running in to is that I cannot select MAX() as that will return the highest product bought on that order.

I am just at a loss here. I hope my explanation is clear.

Any ideas?

P.S. - I can't use subqueries...