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Data & Analytics · Intermediate

Entity Integrity

The relational rule that every table has a primary key and that no primary key value is NULL or duplicated.

Definition

Entity integrity ensures every row can be uniquely identified. It is enforced by the PRIMARY KEY constraint. Together with referential and domain integrity, it is one of the classic integrity types in relational theory.

Exam tip

If an answer choice mentions NULLs in a primary key, it violates entity integrity.

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