adding posts externally: assigning a category?

Hello,
I’m adding wordpress posts externally for a project I’m toying with, with great success. However, assigning the post to a category is not working for me right now. Do you see anything wrong with the query below?:

"INSERT INTO wp_term_relationships (object_id, term_taxonomy_id, term_order) VALUES ('" . $postID . "','" . $categoryID . "','0')"

Thanks much for the assistance! I’m digging through wordpress files now to try to find this and will post if I find something first.