Keys

• A key helps define entity relationships.

• The key’s role is based on a concept known as determination, which is used in the definition of functional dependence.

  • The attribute B is functionally dependent on A if A determines B.
  • An attribute that is part of a key is known as a key attribute.
  • A multi-attribute key is known as a composite key.
  • If the attribute (B) is functionally dependent on a composite key (A) but not on any subset of that composite key, the attribute (B) is fully functionally dependent on (A).

Previous slide

Next slide

Back to first slide

View graphic version