functional dependency


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Related to functional dependency: normalization, Transitive dependency

functional dependency

(database)
Given a relation R (in a relational database), attribute Y of R is functionally dependent on attribute X of R and X of R functionally determines Y of R (in symbols R.X -> R.Y) if and only if each X in R has associated with it precisely one Y in R (at any one time). Attributes X and Y may be composite.

This is very close to a function in the mathematical sense.

functional dependency

A dependent relationship between two data elements in a relational database. Used to define normalization, a functional dependency (FD) states that one data element is dependent on another. For example, a social security number (SSN) refers to only one employee (EMP). Expressed as SSN->EMP, employee is dependent on social security number. A product number refers to one product (PRODNO->PRODNAME), and a customer number refers to one customer name (CUSTNO->CUSTNAME). See normalization and transitive dependency.
References in periodicals archive ?
The evaluation of disability and its ascription and tabulation in the frame of a classification such as the International Functionality, Disability and Health Classification allow us to early identify physical, mental or relational disability areas that may evolve to a functional dependency.
Understanding the relationship between APTI, LOS and functional dependency is important.
k])/A conforming to an XML schema S = (r, L, Ter, p) is an XML functional dependency (XFD) over S.
The results of the selectivity-corrected least squares regression of functional dependency six weeks post-discharge on the amount of the two types of postacute care, controlling for prior patient cognitive and functional status, DRG, race, and illness severity, are summarized in Table 6.
It is important to notice that a data relatability dependency is related to a functional dependency.

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