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In contrast, the 5NF design excludes the possibility of such inconsistencies. A table T is in fifth normal form (5NF) or projection-join normal form (PJ/NF) if it cannot have a lossless decomposition into any number of smaller tables. The case where all the smaller tables after the decomposition have the same candidate key as the table T is ...
Database normalization is the process of structuring a relational database in accordance with a series of so-called normal forms in order to reduce data redundancy and improve data integrity. It was first proposed by British computer scientist Edgar F. Codd as part of his relational model .
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In database normalization, unnormalized form (UNF or 0NF), also known as an unnormalized relation or non-first normal form (N1NF or NF 2), [1] is a database data model (organization of data in a database) which does not meet any of the conditions of database normalization defined by the relational model.
Essential tuple normal form (ETNF) is a normal form used in database normalization.It lies strictly between fourth normal form (4NF) and fifth normal form (5NF). As per the original paper, ETNF, although strictly weaker than 5NF, is exactly as effective as 5NF in eliminating redundancy of tuples.
Domain-key normal form (DK/NF or DKNF) is a normal form used in database normalization which requires that the database contains no constraints other than domain constraints and key constraints. A domain constraint specifies the permissible values for a given attribute, while a key constraint specifies the attributes that uniquely identify a ...
The sixth normal form is currently as of 2009 being used in some data warehouses where the benefits outweigh the drawbacks, [9] for example using anchor modeling.Although using 6NF leads to an explosion of tables, modern databases can prune the tables from select queries (using a process called 'table elimination' - so that a query can be solved without even reading some of the tables that the ...
Model 204 is commonly used in government and military applications. [8] [9] [10]It was used commercially in the UK by Marks & Spencer. [citation needed] It was also used at the Ventura County Property Tax system in California, [11] the Harris County, Texas, Justice Information Management System, [12] and in the New York City Department of Education's Automate The Schools system.