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copied!<blockquote> <p>In the field of relational database design, normalization is a systematic way of ensuring that a database structure is suitable for general-purpose querying and free of certain undesirable characteristics—insertion, update, and deletion anomalies—that could lead to a loss of data integrity.[1] E.F. Codd, the inventor of the relational model, introduced the concept of normalization and what we now know as the first normal form in 1970.[2] Codd went on to define the second and third normal forms in 1971,[3] and Codd and Raymond F. Boyce defined the Boyce-Codd normal form in 1974.[4] Higher normal forms were defined by other theorists in subsequent years, the most recent being the sixth normal form introduced by Chris Date, Hugh Darwen, and Nikos Lorentzos in 2002.[5]</p> <p>Informally, a relational database table (the computerized representation of a relation) is often described as "normalized" if it is in the third normal form (3NF).[6] Most 3NF tables are free of insertion, update, and deletion anomalies, i.e. in most cases 3NF tables adhere to BCNF, 4NF, and 5NF (but typically not 6NF).</p> <p>A standard piece of database design guidance is that the designer should create a fully normalized design; selective denormalization can subsequently be performed for performance reasons.[7] However, some modeling disciplines, such as the dimensional modeling approach to data warehouse design, explicitly recommend non-normalized designs, i.e. designs that in large part do not adhere to 3NF.[8]</p> </blockquote> <p><strong>Edit:</strong> Source: <a href="http://en.wikipedia.org/wiki/Database_normalization" rel="nofollow noreferrer">http://en.wikipedia.org/wiki/Database_normalization</a></p>

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