Answering Queries Using Views
Rada Chirkova, Foto Afrati
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Naturwissenschaften, Medizin, Informatik, Technik / Informatik, EDV
The topic of using views to answer queries has been popular for a few decades now, as it cuts across domains such as query optimization, information integration, data warehousing, website design and, recently, database-as-a-service and data placement in cloud systems.
This book assembles foundational work on answering queries using views in a self-contained manner, with an effort to choose material that constitutes the backbone of the research. It presents efficient algorithms and covers the following problems: query containment; rewriting queries using views in various logical languages; equivalent rewritings and maximally contained rewritings; and computing certain answers in the data-integration and data-exchange settings. Query languages that are considered are fragments of SQL, in particular select-project-join queries, also called conjunctive queries (with or without arithmetic comparisons or negation), and aggregate SQL queries.
This second edition includes two new chapters that refer to tree-like data and respective query languages. Chapter 8 presents the data model for XML documents and the XPath query language, and Chapter 9 provides a theoretical presentation of tree-like data model and query language where the tuples of a relation share a tree-structured schema for that relation and the query language is a dialect of SQL with evaluation techniques appropriately modified to fit the richer schema.
equivalent query rewritings, query containment, XPath, the chase algorithm query containment and rewriting under dependencies, maximally contained query rewritings, tree data, determinacy, arithmetic comparisons, tuple-generating dependencies, acyclic queries, negation, equality-generating dependencies, query equivalence, data exchange, conjunctive queries, aggregate queries