Question

The _________ states that a foreign key must either match a primary key value in another relation or it must be null.

• A. Entity integrity rule
• B. Referential integrity constraint
• C. Action assertion
• D. Composite attribute

Answer 1

Answer: (B)

Referential integrity constraint

Referential integrity is a property of data stating references within it are valid. For referential integrity to hold in a relational database, any column in a base table that is declared a foreign key can contain either a null value, or only values from a parent table's primary key or a candidate key.