Abstract:
Relational database systems do not effectively support complex queries containing quantifiers (quanti-fied queries). Quantified queries are becoming increasingly important in decision support applications in general, and health-care information systems in particular. Recently, it has been shown that generalized quantifiers provide an effective way of expressing such queries naturally, and that generalized quantifiers can be efficiently supported in query processors. In this paper, we present unnesting and optimization techniques for an extended-SQL language, that supports generalized quantifier constructs, to translate extended-SQL queries to algebraic expressions. We introduce a new algebraic operator that captures the operational semantics of a wide range of generalized quantifiers. Furthermore, our optimization technique can also be applied during the unnesting of conventional nested SQL queries. 1
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