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Note for Database Management System - DBMS By Tejas Shenoy

  • Database Management System - DBMS
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Tejas Shenoy
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Normalization Normalization We discuss four normal forms: first, second, third, and Boyce-Codd normal forms 1NF, 2NF, 3NF, and BCNF Normalization is a process that “improves” a database design by generating relations that are of higher normal forms. The objective of normalization: “to create relations where every dependency is on the key, the whole key, and nothing but the key”. 91.2914 1

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Normalization There is a sequence to normal forms: 1NF is considered the weakest, 2NF is stronger than 1NF, 3NF is stronger than 2NF, and BCNF is considered the strongest Also, any relation that is in BCNF, is in 3NF; any relation in 3NF is in 2NF; and any relation in 2NF is in 1NF. 91.2914 2

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Normalization 1NF a relation in BCNF, is also in 3NF 2NF a relation in 3NF is also in 2NF 3NF a relation in 2NF is also in 1NF BCNF 91.2914 3

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Normalization We consider a relation in BCNF to be fully normalized. The benefit of higher normal forms is that update semantics for the affected data are simplified. This means that applications required to maintain the database are simpler. A design that has a lower normal form than another design has more redundancy. Uncontrolled redundancy can lead to data integrity problems. First we introduce the concept of functional dependency May 2005 91.2914 4

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