15.00 - Functional, Transitive, and Multivalued Dependencies - Teradata Database

Teradata Database Design

prodname
Teradata Database
vrm_release
15.00
category
User Guide
featnum
B035-1094-015K

Functional, Transitive, and Multivalued Dependencies

Definitions

 

Term

Definition

Determinant

For any relation R, the set of attributes X in the functional dependency X Y is the determinant group for the dependency.

Full functional dependence

An attribute set X is fully functionally dependent on another attribute set Y if X is functionally dependent on the whole set of Y, but not on any subset of Y.

Functional dependence

For any relation R, attribute X is functionally dependent on attribute Y if for every valid instance, the value of Y determines the value of X.

The symbolic notation for this is Y   X.

Multivalued dependence

For any relation R with attribute set (X,Y,Z), the set X multivalue determines the set Y if, for every pair of tuples containing duplicates in X, the instance also contains the pair of tuples obtained by interchanging the Y tuples in the original pair.

The symbolic notation for this is X  Y.

Transitive dependence

Transitive dependencies are dependencies that exist among three or more attributes in a relation in such a way that one attribute determines a third by way of an intermediate attribute. For example, consider the relation R(X,Y,Z), where X is the primary key.

Attribute Z is transitively dependent on attribute X if attribute Y satisfies the following dependencies, where the symbol  indicates does not determine:

  • X  Y
  • Y  Z
  • Y  X