In: Computer Science
FUNCTIONAL DEPENDENCY
- Functional dependency describes the relationship between attributes in a Database Management System.
- Functional Dependency helps us to maintain the quality of a database
A | -------------------> | B |
- The above representation depicts A is functionally dependant on B.
- denoted by A----> B , if each value of A is associated with exactly one value of B
- A and B may contain one or more attributes
Example:-
For a relation, PersonID functionally determine BirthDate. That is the functional dependancy can be shown as:
PersonID ---------------------> BirthDate
In the above relation, there is exactly one BirthDate for given instance of a person. Note that converse may or may not be true. Many people may have same birthdates. For a given BirthDate , we may find many PersonID sharing the same BirthDate
Functional dependencies are divided into transitive , trivial and multivalued