Joe Celko’s Trees and Hierarchies in SQL for Smarties: A book devoted to nothing but representing hierachies and trees in relational (SQL) databases. Am I a dork because I want it?
In this book, Celko illustrates several major approaches to representing trees and hierarchies and related topics that should be of interest to the working database programmer. These topics include hierarchical encoding schemes, graphs, IMS, binary trees, and more.
I paged through it at the bookstore. It’s heavy on the nested set theory, rather than parent-child.