Database Reference
In-Depth Information
2.
Determine whether each table complies with the Elements of the Ideal Table.
Make certain you resolve all the anomalies you identify in the fields or within the
table structure as a whole.
3.
Establish subset tables as appropriate.
Make certain you properly identify these
tables and add them to the Final Table List as well.
As you complete your review of the tables, you determine that all of them conform to the
Elements of the Ideal Table with the exception of the INVOICES table. The only problem
withthistableisthatitcontainsanunnecessaryduplicatefield:C
UST
H
OME
P
HONE
.Youcan
remove this field from the table, however, because it provides only reference information.
Asyouworkwith the PRODUCTS table, younotice that there are fields youmight be able
to remove and then use as the basis for a subset table. So you review the table once again.
Figure 7.37
shows the PRODUCTS table structure you're currently examining. (This is an
expanded version of the table structure shown in
Figure 7.36
.
)
Figure 7.37. The PRODUCTS table structure (expanded version)
Your assumption proves correct. You determine that certain fields describe a service, and
you can construe a service as being a different type of product. A service is similar to
a product in that it has a name, description, and category, but it is different inasmuch as
it has a type, materials charge, service charge, and service date. With this in mind, you
