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The objectives of normalization beyond 1NF (first normal form) were stated by Codd as: To free the collection of relations from undesirable insertion, update and deletion dependencies. To reduce the need for restructuring the collection of relations, as new types of data are introduced, and thus increase the life span of application programs.
For example, appending addresses with any phone numbers related to that address. Data cleansing may also involve harmonization (or normalization) of data, which is the process of bringing together data of "varying file formats, naming conventions, and columns", [ 2 ] and transforming it into one cohesive data set; a simple example is the ...
The purpose of this normalization is to increase flexibility and data independence, and to simplify the data language. It also opens the door to further normalization, which eliminates redundancy and anomalies. Most relational database management systems do not support nested records, so tables are in first normal form by default.
Fourth normal form (4NF) is a normal form used in database normalization. Introduced by Ronald Fagin in 1977, 4NF is the next level of normalization after Boyce–Codd normal form (BCNF). Whereas the second , third , and Boyce–Codd normal forms are concerned with functional dependencies , 4NF is concerned with a more general type of ...
Fifth normal form (5NF), also known as projection–join normal form (PJ/NF), is a level of database normalization designed to remove redundancy in relational databases recording multi-valued facts by isolating semantically related multiple relationships.
An example of a data-integrity mechanism is the parent-and-child relationship of related records. If a parent record owns one or more related child records all of the referential integrity processes are handled by the database itself, which automatically ensures the accuracy and integrity of the data so that no child record can exist without a parent (also called being orphaned) and that no ...
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