Database Reference
In-Depth Information
Why You Should Review Data Integrity
You're probably wondering why you should review the database structure one last time,
given that you've paid attention to every detail and have focused on data integrity
throughout the entire design process. The answer is simple: You want to make certain that
the data integrity you've been so careful to establish is absolutely as sound as possible. As
you well know, a crack in the integrity could result in inconsistent data or inaccurate in-
formation. However improbable, it is possible that you may have overlooked something.
The peace of mind you gain from knowing that you have a solidly designed database is
well worth the investment of your time and effort of this final review.
Note
Remember: Garbage in, garbage out!
Reviewing and Refining Data Integrity
Reviewing data integrity is a simple task if you take a modular approach, that is, if you
sequentially review each component of overall data integrity: table-level, field-level, and
relationship-level integrity and business rules. You should encounter very few problems
here if you have carefully followed the design method presented in this topic. The follow-
ing sections briefly outline the points you should keep in mind as you conduct the review,
and they contain references to earlier chapters in case you encounter any problems.
Table-Level Integrity
In order to ensure that you've properly established table-level integrity, review each table
and make certain that the table conforms to all of the following points.
• There are no duplicate fields in the table.
• There are no calculated fields in the table.
• There are no multivalued fields in the table.
• There are no multipart fields in the table.
• There are no duplicate records in the table.
• Every record in the table is identified by a primary key value.
• Each primary key conforms to the Elements of a Primary Key.
If you believe you have problems with any of these items, resolve them using the tech-
niques and concepts discussed in
Chapter 6
,
“
Analyzing the Current Database
,”
Chapter 7
,
“
Establishing Table Structures
,” and
Chapter 8
,
“
Keys
.”
