In this series of articles, I'm discussing various classes of custom-aggregation solutions. SQL Server's built-in aggregate functions (e.g.,AVG, COUNT, MAX, MIN, SUM) are admittedly useful, but what if you need other types of aggregations that SQL Server doesn't provide? In the series' first two articles—"Custom Aggregations: The CursorTechnique" (http://www.sqlmag.com, March 2006, InstantDoc ID 49038) and "Custom Aggregations: The Pivoting Technique" (May 2006, InstantDoc ID 49675), I dis...