Materialized Views

Materialized views are queries whose results are stored and maintained in order to facilitate access to data in their underlying base tables. In the SQL setting, they are now considered a mature technology implemented by most commercial database systems and tightly integrated into query optimization. They have also helped lay the foundation for important topics such as information integration and data warehousing. This monograph provides an introduction and reference to materialized views. We cover three fundamental problems: (1) maintaining materialized views efficiently when the base tables change, (2) using materialized views effectively to improve performance and availability, and (3) selecting which views to materialize. We also point out their connections to a few other areas in database research, illustrate the benefit of cross-pollination of ideas with these areas, and identify several directions for research on materialized views.