Database Reference
In-Depth Information
Field-Level Integrity
Afieldattains
field-level integrity
afteryou'vedefinedacompletesetoffieldspecifications
for the field. Field-level integrity warrants the following.
• The identity and purpose of a field is clear, and all of the tables in which it appears
are properly identified.
• Field definitions are consistent throughout the database.
• The values of a field are consistent and valid.
• The types of modifications, comparisons, and operations that can be applied to the
values in the field are clearly identified.
Youcanguaranteethatafieldstructureissoundandoptimallydesignedwhenithasacom-
plete set of field specifications and fully conforms to the Elements of the Ideal Field. In
fact, ensuring that the field complies with the Elements of the Ideal Field makes defining a
set of specifications a relatively easy task.
If you've had any lingering doubt about a particular field's conformance to the Elements
of the Ideal Field, now is a good time to review that field once more. If you determine that
it is
not
in conformance, use the appropriate techniques to resolve the problem and make
the proper adjustments to the table; otherwise, you can begin the process of defining field
specifications for each field in the database. Here are the Elements of the Ideal Field once
again for your convenience.
• It represents a distinct characteristic of the subject of the table.
• It contains only a single value.
• It cannot be deconstructed into smaller components.
• It does not contain a calculated or concatenated value.
• It is unique within the entire database structure.
• It retains a majority of its characteristics when it appears in more than one table.
Anatomy of a Field Specification
A field specification incorporates various elements that define every attribute of a field.
All of the elements within the specification are categorized as
general elements, physical
elements,
or
logical elements.
These element categories enable you to focus on a distinct
aspect of the field as you're defining the specification, and they provide a way for you to
find a particular element quite easily.
Here are the elements within each category.
