Database Reference
In-Depth Information
Figure 9.7. The Logical Elements category for an E
MPLOYEE
ID N
UMBER
field
Using Unique, Generic, and Replica Field Specifications
Earlierinthischapter,youlearnedthatyoucoulddefineaspecificationas
Unique, Generic,
or
Replica.
You can ensure that you define the appropriate type of specification for a given
field by following these simple guidelines.
• Use a
Unique
specification for any field that will appear only once within the en-
tire database or for a field that serves as a
primary key.
• Use a
Generic
specification for a field that serves as a template for other fields
within the database. Remember to use a nonspecific field name and element set-
tings that are as broad and general as possible.
• Use a
Replica
specification for a field that you base on a given generic field or for
a field that serves as a foreign key within a table relationship.
