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Explaining the complete concepts that lie behind the different normal forms is beyond
the scope of this chapter and book.
Data Design | 103
1. Identify the objects your application needs to know (the entities). Examples of
entities, as shown in Figure 4-3, include employees, locations, and jobs.
2. Identify the individual pieces of data, referred to by data modelers as attributes,
for these entities. In Figure 4-3, employee name and salary are attributes. Typically,
entities correspond to tables and attributes correspond to columns.
3. As a potential last step in the process, identify relationships between the entities
based on your business. These relationships are implemented in the database
schema through the use of a combination known as a foreign key. For example,
the primary key of the DEPARTMENT NUMBER table would be a foreign key
column in the EMPLOYEE NAME table used to identify the DEPARTMENT
NUMBER in which an employee works. A foreign key is a type of constraint;
constraints are discussed later in this chapter.


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