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Database normalization (or normalisation) is the process of organizing the columns (attributes) and tables (relations) of a relational database to minimize data redundancy. Normalization involves decomposing a table into less redundant (and smaller) tables without losing information; defining foreign keys in the old table referencing the primary keys of the new ones. The objective is to isolate data so that additions, deletions, and modifications of an attribute can be made in just one table and then propagated through the rest of the database using the defined foreign keys. Edgar F. Codd, the inventor of the relational model (RM), introduced the concept of normalization and what we now know as the First normal form (1NF) in 1970. Codd went on to define the Second normal form (2NF) and Third normal form (3NF) in 1971,〔Codd, E.F. "Further Normalization of the Data Base Relational Model". (Presented at Courant Computer Science Symposia Series 6, "Data Base Systems", New York City, May 24–25, 1971.) IBM Research Report RJ909 (August 31, 1971). Republished in Randall J. Rustin (ed.), ''Data Base Systems: Courant Computer Science Symposia Series 6''. Prentice-Hall, 1972.〕 and Codd and Raymond F. Boyce defined the Boyce-Codd Normal Form (BCNF) in 1974.〔Codd, E. F. "Recent Investigations into Relational Data Base Systems". IBM Research Report RJ1385 (April 23, 1974). Republished in ''Proc. 1974 Congress'' (Stockholm, Sweden, 1974). , N.Y.: North-Holland (1974).〕 Informally, a relational database table is often described as "normalized" if it meets Third Normal Form.〔C.J. Date. ''An Introduction to Database Systems''. Addison-Wesley (1999), p. 290〕 Most 3NF tables are free of insertion, update, and deletion anomalies. The relational model separates the logical design from the physical design: DBMS performance is a matter of physical design using indexes, view materialization, big buffers, etc. It is not a matter of changing the logical design. A typical example of normalization is that an entity's unique ID is stored everywhere in the system but its name is held in only one table. The name can be updated more easily in one row of one table. A typical update in such an example would be the RIM company changing its name to BlackBerry. That update would be done in one place and immediately the correct "BlackBerry" name would be displayed throughout the system. ==Objectives== A basic objective of the first normal form defined by Codd in 1970 was to permit data to be queried and manipulated using a "universal data sub-language" grounded in first-order logic.〔"The adoption of a relational model of data ... permits the development of a universal data sub-language based on an applied predicate calculus. A first-order predicate calculus suffices if the collection of relations is in first normal form. Such a language would provide a yardstick of linguistic power for all other proposed data languages, and would itself be a strong candidate for embedding (with appropriate syntactic modification) in a variety of host Ianguages (programming, command- or problem-oriented)." Codd, ("A Relational Model of Data for Large Shared Data Banks" ), p. 381〕 (SQL is an example of such a data sub-language, albeit one that Codd regarded as seriously flawed.)〔Codd, E.F. Chapter 23, "Serious Flaws in SQL", in ''The Relational Model for Database Management: Version 2''. Addison-Wesley (1990), pp. 371–389〕 The objectives of normalization beyond 1NF (First Normal Form) were stated as follows by Codd: The sections below give details of each of these objectives. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「database normalization」の詳細全文を読む スポンサード リンク
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