Note: The solutions presented in this article require SQL Server 2005 Beta 1 or higher. They were developed and tested on a pre-release version of SQL Server 2005 Beta 2 by Lubor Kollar and Itzik Ben-Gan.

Imagine that you need to know whether one person is an ancestor of another person. A data structure called transitive closure can help. For example, Fosco Baggins is the father of Drogo, and Drogo is the father of Frodo; therefore, Fosco is an ancestor of Frodo by transitivity. Simply ...