# How Normalization Can Be Used To Check Relations

Essay by 24 • October 13, 2010 • 464 Words (2 Pages) • 1,310 Views

**Page 1 of 2**

How Normalization Can Be Used to Check Relations

Data normalization is a technique used during logical data modeling to ensure that there is only one way to know a fact, by removing all structures that provide more than one way to know the same fact as represented in a database relation (table).

There are six generally recognized normal forms of a relation: first normal form, second normal form, third normal form, Boyce/Codd normal form, fourth normal form, and fifth normal form, also called projection/join normal form. Other normal forms (e.g., Domain/Key) exist but will not be discussed here. The normal forms are hierarchical, i.e., each normal form builds upon its predecessor. Although many people consider a relation to be normalized only when it is in third normal form, technically speaking, a relation in only first normal form can be considered normalized.

The following definitions represent the rules used in normalization to check database relations:

Functional dependency - Functional dependency analysis is a tool for logically organizing related attributes and for determining a relation's primary key. Functional dependency analysis is the main tool for constructing normalized relations. Functional dependence is defined as: For any relation R, attribute A is fully functionally dependent on attribute B if, for every valid instance, the value of B determines the value of A.

Multivalued dependency - Multivalued dependencies can occur when the attributes within a relation are not logically related to each other. Date's "formal" definition says: Let R be a relation, and let A, B, and C be arbitrary subsets of the set of attributes of R. We then say that A multidetermines B only if one of the set of B values match a given (A, C) pair in R and depends only on the A value and is not dependent on the C value.

Trivial dependency - A dependency is trivial

...

...

(2010, 10). How Normalization Can Be Used To Check Relations. *Essays24.com*. Retrieved 10, 2010, from https://www.essays24.com/essay/How-Normalization-Can-Be-Used-To-Check-Relations/4135.html

"How Normalization Can Be Used To Check Relations" __Essays24.com__. 10 2010. 2010. 10 2010 <https://www.essays24.com/essay/How-Normalization-Can-Be-Used-To-Check-Relations/4135.html>.

"How Normalization Can Be Used To Check Relations." *Essays24.com*. Essays24.com, 10 2010. Web. 10 2010. <https://www.essays24.com/essay/How-Normalization-Can-Be-Used-To-Check-Relations/4135.html>.

"How Normalization Can Be Used To Check Relations." Essays24.com. 10, 2010. Accessed 10, 2010. https://www.essays24.com/essay/How-Normalization-Can-Be-Used-To-Check-Relations/4135.html.