DATA NORMALIZATION METHOD - Database Design and Development: An Essential Guide for IT Professionals - page 319

Remove
partial key
dependencies

Remove
repeating
groups

First
Normal
Form

Table with
repeating
groups

Remove key
component
dependencies

Remove
transitive
dependencies

Third
Normal
Form

Second
Normal
Form

Boyce-
Codd
Normal
Form

Fourth
Normal
Form

Remove
multivalued
dependencies

Remove
join
dependencies

Fifth
Normal
Form

Express business
rules and
relationships

Domain-Key
Normal Form

Figure 10-14 Normalization summary.

What exactly do you accomplish in the first set of steps refining the data model
into the fundamental normal forms? In the relational data model, for every rela-
tion, each attribute must functionally depend only on the full primary key. There
should not be any other type of functional dependencies. Update, deletion, and addi-
tion anomalies are caused by incorrect functional dependencies within a relation.
Once you complete the first set of steps to produce the fundamental normal forms,
all problems of invalid functional dependencies are removed.
The second set of normalization steps considers other types of dependencies.
Such dependency problems are rare in practice. For that reason, the fundamental
normal forms are more important.
Figure 10-14 summarizes the normalization steps. Note the two sets of steps pro-
ducing the two types of normal forms—fundamental normal forms and higher
normal forms. In each step, you tackle one and only one type of problem. The result
in each step is a progression toward the final true relational data model.

Critical Issues

Before we end our discussion of the normalization approach, it is worthwhile to list
a few critical issues to be concerned about. Give careful consideration to the fol-
lowing points.

• Remember that the normalization method begins with an intuitive data model.
• If the scope of the real-world information is too large or complex and you are
not able to create a complete initial data model intuitively, then do not pursue
this method.
• Each normalization step focuses on only one type of problem. Make sure you
look for the appropriate type of problem in each step.
• The normalization process follows a predefined sequence of steps. Follow the
steps in sequence for best results.