<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.
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Nearby terms: function « functional « functional database « functional dependency » functionality » functional language » functional program