Establishing Table Structures - Database Design for Mere Mortals - page 158

Refining the Fields
Now that you've assigned fields to each table, you'll refine the fields by improving the
field names and resolving any structural problems that may exist. Then you'll refine the
tables further by establishing that you've assigned the appropriate fields to each table and
that the table structures are sound.
Improving the Field Names
As you know, a field represents a characteristic of the subject of the table to which it be-
longs. You can easily identify the characteristic a field is supposed to represent when that
field has an appropriate name. A field name that is ambiguous, vague, or unclear is a sure
signoftroubleandsuggeststhatyouhavenotthoroughlyidentifiedthepurposeofthefield.
Earlier in this chapter, you learned a set of guidelines for naming a table. Now you'll learn
another set of guidelines that you'll apply to field names. Fortunately, many of them are
similartotheguidelinesgoverningtablenames,soyou'realreadyfamiliarwithmostofthe
concepts.
Guidelines for Creating Field Names
• Create a unique, descriptive name that is meaningful to the entire organization. A
given field name should appear only once in the entire database; the only excep-
tion to this rule occurs when the field serves to establish a relationship between
two tables. Make certain the name is descriptive enough to convey its meaning ac-
curately to everyone who sees it. ( Chapter 10 covers this issue in greater detail.)
• Create a name that accurately, clearly, and unambiguously identifies the charac-
teristic a field represents. “Phone Number” is a good example of an inaccurate,
ambiguous field name. What kind of phone number does it represent? A home
phone? An office phone? A cellular phone? Learn to be specific. If you need to re-
cord each of these types of phone numbers, then create “Home Phone,” “Work
Phone,” and “Cellular Phone” fields.
In Chapter 6 , “ Analyzing the Current Database ,” you learned how to resolve gen-
eric field names, such as “Address,” “City,” and “State,” by using the table name
as a prefix for the field name. This produces names such as “ Employee Address,”
“ Customer Address,” and “ Supplier Address.” When you have field names such as
these, you can abbreviate the prefix (for brevity's sake) by using the first three or
four letters of the table name as the revised prefix. This allows you to transform
the previous field names into “ Emp Address,” “ Cust Address,” and “ Supp Address.”
This technique helps you fulfill not only this guideline, but the previous one as
well.