lec06.366

lec06.366 - . . Winter 2008 CPE/CSC 366: Database Modeling,...

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Unformatted text preview: . . Winter 2008 CPE/CSC 366: Database Modeling, Design and Implementation Alexander Dekhtyar . . Theory of Normal Forms Functional Dependencies in Databases Functional Dependencies Functional dependencies allow identify redundancy in relational database schemas. A functional dependency (FD) on a relation R is a statement of the form: If two tuples agree on all attributes A 1 ,...,A n then they must also agree on all attributes B 1 ,...,B m . A functional dependency is formally denoted as A 1 ,...,A n B 1 ,...,B m We also say A 1 ,...,A n functionally determine B 1 ,...,B m . Keys and Superkeys Functional dependencies allow us to formalize the definition of a key in a rela- tional table. A set of one or more attrbiutes A 1 ,...,A n of relational table R is a key of R if: 1. A 1 ,...,A n B for all attributes B of R . (i.e., A 1 ,...,A n functionally determine all attributes of R ). 2. No proper subset of A 1 ,...,A n functionally determines all at- tributes of R ....
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This note was uploaded on 05/19/2008 for the course CSC 365 taught by Professor Dekhtyar during the Spring '08 term at Cal Poly.

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lec06.366 - . . Winter 2008 CPE/CSC 366: Database Modeling,...

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