A database contains an entry with an empty primary key. What database concept has been violated?

A.
Entity Integrity

B.
Normalization

C.
Referential Integrity

D.
Semantic Integrity

Explanation:
Answer A is correct; Entity integrity means each tuple has a unique primary key that is not null.

Incorrect Answers and Explanations: B, C, and D: Answers B, C, and D are incorrect. Normalization seeks to make the data in a database table logically concise, organized and consistent. Referential integrity means that every foreign key in a secondary table matches a primary key in the parent table: if this is not true, referential integrity has been broken. Semantic integrity means each attribute (column) value is consistent with the attribute data type.