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Data & Analytics · Intermediate

Natural Key

A key made from real-world business data that is already unique, such as an ISBN, VIN or email address; also called a business key.

Definition

Natural keys carry meaning to users and exist outside the database. They can change or be reused, and they may be wide, which is why designers often add a surrogate key and keep the natural key as an alternate key.

Example

Using ISBN as the primary key of a Books table.

Exam tip

Watch for scenarios where a 'unique' business value can change, such as an email address; that points to using a surrogate key instead.

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