Joe Celko's Trees and Hierarchies in SQL for Smarties

CHAPTER 11 Hierarchical Encoding Schemes

AHIERARCHY IS A useful concept for classifying data, as well as retrieving it. The encoding schemes used to represent data are often hierarchical. Tree structures are a natural way to model encoding schemes that have a natural hierarchy. They organize the data for searching and reporting along that natural hierarchy and make it very easy for a human being to understand. But, what do you use for this natural organizational principle? Physical, temporal, or procedural options often exist, but many hierarchical encoding schemes are more circumstantial, traditional, and just plain arbitrary.

11.1 ZIP codes

The most common example of a hierarchical encoding scheme is the ZIP code, which partitions the United ...