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Databases Illuminated, 4th Edition
book

Databases Illuminated, 4th Edition

by Catherine M. Ricardo, Susan D. Urban, Karen C. Davis
March 2022
Intermediate to advanced content levelIntermediate to advanced
682 pages
22h 58m
English
Jones & Bartlett Learning
Content preview from Databases Illuminated, 4th Edition

6.3 Functional Dependency (FD)

A functional dependency (FD) is a type of relationship between attributes, as described in the following definition:

Definition: If R is a relation schema and A and B are non-empty sets of attributes in R, we say that B is functionally dependent on A if, and only if, each value of A in R has associated with it exactly one value of B in R.

We write this as

A right arrow B.

which we read as “A functionally determines B.” The definition says that if two tuples in an extension of R have the same value for A, they must also have the same values for B. More formally, for every pair of tuples, t1 and t2, in every instance of R, we have ...

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Publisher Resources

ISBN: 9781284231595