A database is a collection of related information and it is therefore inevitable that some items of information in the database would depend on some other items of information. The information is either single-valued or multivalued. The name of a person or his date of birth is single-valued facts; qualifications of a person or subjects that an instructor teaches are multivalued facts. We will deal only with single-valued facts and discuss the concept of functional dependency.
Let us describe this concept logically.