'Tuple variable' diaporamas de présentation

Distributed Database Management System

Distributed Database Management System. Lecture 8. Semijoin. S =. R. ? A?B (S). F. R. F. Subset of tuples of R that participate in join of R with S. Division. The division of R with degree r with S with degree s is the set of (r-s)-tuples t such that.

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Introduction to SQL

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Relational Calculus

Relational Calculus. Objectives. Introduction + Tuple Relational Calculus + Domain relational Calculus + QBE +. - Introduction. Relational calculus is a formal query language where we write one declarative expression to specify a retrieval request.

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The Relational Calculus

The Relational Calculus. The Relational Calculus. The Relational Calculus High-level, non-procedural language Relational calculus expression declares the requirements tuples in the resulting relation must satisfy. Provides foundation for standard query language (SQL) Expressive power

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Relational Calculus

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TRC vs DRC

TRC vs DRC. 2003. 10. 12 ???. Queries in TRC and DRC. TRC Q = {t| f(t)} where t is a (free) tuple variable and f(t) is a well-formed formula DRC Q = {x 1 ,x 2 ,..,x k | f(x 1 ,x 2 ,..,x k )} where x i is a (free) domain variable and f(x 1 ,x 2 ,..,x k ) is a well-formed formula.

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TRC vs DRC

TRC vs DRC. 2003. 10. 12 ???. Queries in TRC and DRC. TRC Q = {t| f(t)} where t is a (free) tuple variable and f(t) is a well-formed formula DRC Q = {x 1 ,x 2 ,..,x k | f(x 1 ,x 2 ,..,x k )} where x i is a (free) domain variable and f(x 1 ,x 2 ,..,x k ) is a well-formed formula.

145 views • 8 slides