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.