Database Reference
In-Depth Information
Chapter VII
Normalization of
Relations with Nulls in
Candidate Keys:
Traditional and Domain
Key Normal Forms
George C. Philip, University of Wisconsin Oshkosh, USA
ABSTRACT
This chapter discusses normalization of relations when the candidate keys of a relation have
missing information represented by nulls. The chapter shows that problems and confusion
can arise in normalizing relations with nulls in candidate keys. Candidate keys with miss-
ing information commonly are found in relations that represent information on two entities
with a one-to-one relationship between them. The current defi nition of Boyce-Codd Normal
one-to-one relationship between them. The current defi nition of
Form (BCNF) is ineffective in identifying poor designs in such relations that may have in-
sertion/deletion anomalies. Domain Key Normal Form (DKNF) also suffers from the same
problem. It is shown that the above problem can be corrected by incorporating the concept
of entity integrity rule into the defi nitions of BCNF and
of entity integrity rule into the defi nitions of DKNF. This chapter also shows that
incorporating the entity integrity rule into the defi nition of either a relation or a candidate
key does not provide a satisfactory solution to the problem.
