Functional Dependency

Topics: Database

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In databases, we have a functional dependency when, in a relation, the values in a set of attributes are determined by the values in another set of attributes.

More formally, a functional dependency occurs between two attributes $X,Y$ in a relation if and only if each value of $X$ is associated with exactly one (and only one) $Y$ value. We write such a functional dependency as $X\to Y$.

Indeed, it’s called a functional dependency because it behaves just like a function; it is a function.