i need to know if i can get child categoreis?

Hi guys i really need soem help on this.

I need to be able to get child categories based on a parent category, and i need to get all the terms globally, from all sub-sites.

I can get the categories, that is not the issue. The problem is that while MarketPress maintains global tables for terms and term_relationships, it doesn't store data for term_taxonomy, which is the table that stores the parent data. Without this table, i can't query by parent item. That means that I can get the categories, but I can't get them by parent category, so i can't build the hierarchy.

anyideas on this please.