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Data & Analytics · Intermediate

Functional Dependency

A relationship where the value of one attribute (or set) uniquely determines the value of another: X -> Y.

Definition

Functional dependencies are the basis of normalization. If EmpID -> Name, every row with the same EmpID has the same Name. Normal forms are defined by which kinds of functional dependencies a table may contain.

Example

ZIP code -> City is a functional dependency in most address data.

Exam tip

Identify the determinant (left side) first; normalization questions hinge on whether it is a key.

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