Designing Views to Efficiently Answer Real SQL Queries

Foto Afrati, Rada Chirkova, Manolis Gergatsoulis, Vassia Pavlaki

Abstract: The problem of optimizing queries in the presence of materialized views and the related view-design problem have recently attracted a lot of attention. Significant research results have been reported, and materialized views are increasingly used in query evaluation in commercial data-management systems. At the same time, most results in the literature assume set-theoretic semantics, whereas SQL queries have bag-theoretic semantics (duplicates are not eliminated unless explicitly requested). This paper presents results on selecting views to answer queries in relational databases under set, bag, and bag-set semantics. The results can be used under each of the three assumptions, to find sound and complete algorithms for designing views and rewriting queries efficiently.
Keywords: Data integration, query transformation, database theory.