Check out this article: http://www.evolt.org/article/Four_ways_to_work_with_hierarchical_data/17/404 7/index.html -joshua HTH > I'm developing a category system that uses a parent-child relationship to create > a flexible hierarchical data structure. IE: > > cat_id PK numeric > parent_id numeric (0 for top-level cats, cat_id for children) > cat_desc varchar2