Database Reference
In-Depth Information
Just as you had guidelines to help define table names, you also have a set of guidelines to
help you compose a table description that is focused, concise, unambiguous, and clear.
Guidelines for Composing a Table Description
•
Include a statement that accurately defines the table.
Anyone should easily be able
to determine the identity of the table from its description without any confusion or
uncertainty. Here's an example of a poor definition for a table named “Suppliers”
in a bakery database. As you can see, it's not very accurate:
Suppliers—the companies that supply us with ingredients and
equipment
What if the bakery receives some of its ingredients from local farmers? The farm-
ers certainly don't qualify as “companies.” What type of equipment do these sup-
pliers supply? Cooking utensils? Hand trucks? Delivery racks? Here's a much bet-
ter definition of suppliers:
Suppliers—the people andorganizations fromwhichwepurchase
ingredients and equipment
This statement can be used in the table description as the
table definition.
•
Include a statement that explains why this table is important to the organization.
A
table contains data that is collected, maintained, manipulated, and retrieved by the
organization for a
particular
reason. Your statement should explain
why
the data is
important to the organization. Keeping in mind that this statement becomes part of
your table description, you might be tempted to construct a statement such as this:
WeneedtheSupplierstabletokeeptrackofthenames,addresses,
phone numbers, and contact names of all our suppliers.
This statement is inadequate because it emphasizes only
what
needs to be stored in
the Suppliers table instead of amplifying
why
the data is important to the business.
The next example conveys a better sense of why the information is important:
Supplier information is vital to the bakery because it allows us
to maintain a constant supply of ingredients and ensure that our
equipment is always in working order.
This is a more effective statement because it conveys the importance of the data by
identifying the services the suppliers provide to the bakery. It also implies that the
bakery could run out of ingredients or have a hard time keeping its equipment in
top shape without the suppliers' services. This statement now reflects why the
table is important to the organization.
