Question

Which integrity constraint guarantees that every primary key attribute is not-null?

Answer 1

not null constraint written with primary key

Answer 2

Concept: Every relation must have a primary key, and the data values for that primary key must all be legitimate, according to the entity integrity rule, which is intended to ensure this. Every main key attribute is guaranteed to be non-null by entity integrity.

• In a relational model, the main key fulfils the unique identification role.
• Entity integrity refers to the fact that an entity that cannot be named is a contradiction in terms.
• When no alternative value applies or when it's unclear what value should be used, the attribute is given a null value.

Given:  every primary key attribute is not-null

To find: Integrity constraint

Solution:

Every main key attribute is guaranteed to be non-null by entity integrity. In a relational model, the main key fulfils the unique identification role. Entity integrity refers to the fact that an entity that cannot be named is a contradiction in terms.

Hence, Entity integrity constraint guarantees that every primary key attribute is not-null.

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