013BSCCSIT039.docx - Tuple Relational Calculus Tuple...

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Tuple Relational CalculusTuple relational calculus is a form of “pure” type of Query Language. Pure languages formunderlying basis of query languages that people use.In brief, TRC is a nonprocedural query language, where each query is of the form:- {t | P (t) }It is the set of all tuples t such that predicate P is true for tt is a tuple variable, t[A] denotes the value of tuple ‘t’ on attribute Atr denotes that tuple t is in relation rP is a formula similar to that of the predicate calculusViewsIn some cases, it is not desirable for all users to see the entire logical model (i.e., allthe actual relations stored in the database.)Consider a person who needs to know a customer’s loan number but has no need tosee the loan amount. This person should see a relation described, in the relationalalgebra, bycustomer-name, loan-number(borrowerloan)Any relation that is not of the conceptual model but is made visible to a user as a“virtual relation” is called a view.View Definition

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Term
Fall
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Tags
Relational model, TRC

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