Creating a Hierarchical Structure

How would you, or what is the commonly accepted way, of creating a database which represents a hierarchical category structure ala Yahoo!?

What I have done until now is to create a table called categories. Each field has a categoryID, a parentID and the category's name. The parentID is "0" for all top level categories, and all sub-categories inherit a parentID containing the categoryID of the category above it. So for instance:

CategoryID     ParentID      Name
       1                     0          Shopping
       2                     1          Retail
       3                     1          Business to Business
       4                     2          Clothing

I was talking to some guy yesterday who said the standard what of creating such a system in a directory was to have a table which contains your root categories and then a new table for every level of sub-category. So if your directory goes 10 levels deep you have 10 category tables each containing the categories of a level.

What's better and why? What do you guys do?

Gabe

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