## 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.

Last updated: 1997-09-01

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**Nearby terms:**

**functional dependency**» functionality » functional language » functional program