Field Specifications - Database Design for Mere Mortals - page 225

Figure 9.1. Field Specifications sheet
General Elements
ItemsundertheGeneralElementscategoryrepresentthemostfundamentalattributesofthe
field. They provide information on the field's purpose, the name of the table(s) in which
the field appears, and the pseudonyms the field assumes under certain circumstances.
Field Name
This is the set of absolute minimal words that uniquely identifies a particular field
throughout the database. You created and refined field names earlier in the database design
process (see Chapter 7 , “ Establishing Table Structures ”), so you'll just take each name and
use it as the setting for this element.
Parent Table
The table that incorporates a given field within its structure is known as the field's parent
table . This isthe onlytable inwhich the field will appear unless the field isparticipating in
establishing a relationship. (You'll learn more about this exception in Chapter 10 , “ Table
Relationships .”)Forexample,STUDENTSistheparenttableoftheS TUD F IRST N AME field.
Label
This is an alternate name (typically a shorter form of the field name) by which you can
identify the field within an end-user application interface that you create for the database.
Forexample,youmightuseQ TY O N H AND asalabelforafieldnamedQ UANTITY O N H AND
because many people in the organization are already accustomed to this particular name.
Labels can be particularly useful when you want to conserve space on a data entry screen
or squeeze more fields into a particular report.
Avoid the temptation of using the label as the official field name within the table structure;
otherwise, you make it possible for someone to misinterpret or incorrectly identify the
field. Always use the most precise and accurate name as the official field name and then
use the label (judiciously, of course) within your end-user interface applications. This will
enable you to make a distinction between the two at all times.
Specification Type
The elements you set for a given field depend upon the type of specification you define for
the field. You can define a specification in three ways.
1. Unique: This is the default specification for all fields except those that serve as a
template for other fields or those that participate within a table relationship as for-
eign keys. You can incorporate all but the Source Specification element for this