Just curious what some of you do when you parse the categories of a merchant. Do you do a true hierachy, a SQL Tree or the like:

id category parent
1 shoes null
2 dress 1
3 boot 2
4 something 2

or do you just create a related table that has something like

productid, name, manufacturer, description, buyurl, imageurl, category1, category2, category3, category4....

or maybe something else.