Database Reference
In-Depth Information
Note
Remember that you're dealing strictly with the
logical
database structure at this
point. You might have cause to duplicate specific fields when you
physically
im-
plementthedatabaseinanRDBMSprogram.Duringthatprocess,however,you're
making a conscious decision to duplicate the fields and you're prepared to deal
with the consequences of that decision.
•
It retains a majority of its properties when it appears in more than one table.
A
field that establishes a relationship between two tables is a structural component of
each table. A majority of the field's properties remain constant in each occurrence
of the field. (
Chapter 9
, “
Field Specifications
,
” and
Chapter 10
cover this matter in
greater detail.)
Although you now know the specific elements of an ideal field, you'll still find it difficult
in many instances to identify problematic fields just by looking at their names.
Figure 7.13
shows a table structure that helps to illustrate this point. Take a moment and try to determ-
ine whether each field complies with the
Elements of the Ideal Field
or needs to be modi-
fied.
