Hi David,

Yes! This is an amazing topic! Joe Celko's technique has saved one big project we run here at the company. Basically, his technique (called adjacency list) stores the tree nodes hierarchies as a Graph and frees you from having to store the parent/child foreing-key references into the relational tables, which, BTW, is very annoying, given the need of several INNER JOIN constructs we have to build in order to retrieve the ancestors/descendents sets.

Here is an article you may find useful until Celko's new book doesn't become available:

http://www.intelligententerprise.com/001020/celko1_1.jhtml

HTH.