Appropriately selected materialized views (also called indexed views) can speed up query execution by orders of magnitude. Most database systems limit support for materialized views to select-project-join expressions, possibly with a group-by, over base tables because this class of views can be efficiently maintained incrementally and thus kept up to date with the underlying source tables. However, limiting views to reference only base tables restricts the class of queries that can be supported by materialized views. View stacking (also called views on views) relaxes one restriction by allowing a materialized view to reference both base tables and other materialized views. This extends materialized view support to additional types of queries. This paper describes a prototype implementation of stacked views within Microsoft SQL Server and explains which classes of queries can be supported. To support view matching for stacked views, a signature mechanism was added to the optimizer. Thi...