First Normal Form (1NF)
First Normal Form (1NF) is a minimal normal form that introduced by E.F. Codd. 1NF must ensure that a table structure is a faithful representation of a relation and that it is free of repeating groups.
E.F. Codd's definition is "values in the domains on which each relation is defined are required to be atomic with respect to the DBMS." E.F. Codd defines an atomic value as one that "cannot be decomposed into smaller pieces by the DBMS (excluding certain special functions)."
1NF is used to identify and eliminate repeating group of data or a repeating group of attributes from one entity that decompose into two different entities to produce atomic data. Atomic data is simplifies SQL Query Operation and the decomposed entities are relates through Relational Join Operator based on common attributes and Primary Key.
An instance, a project development team is formed with many employees and each employee has more than one Technical Skills that information is maintain in the following (Non-First Normal Form) Employee_Master Entity.
This Employee_Master Entity is maintains repeating groups of data in the Emp_Skills attribute. According to the 1NF, the Employee_Master Entity can decompose into Employee_Master and Employee_Skills Entities to produce atomic data.
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