Database Reference
In-Depth Information
it is poorly designed—there may be more effective ways to design and generate the
same report. Queries may run slowly because they are improperly defined. Make
certain that each query is defined correctly and in the most efficient way possible.
If you believe you must depart from proper database design techniques, carefully examine
yoursituation.AsImentionedearlier,it'sacceptabletosuspendtherules
if
youaredesign-
ing an analytical database. But I still strongly recommend that you design your database
properly and thoroughly and relax the rules
only
for very specific reasons.
Documenting Your Actions
Ifyou'veexhaustedallotheroptionsandstillcometotheconclusionthatyouneedtobend
or break the rules, then
you must document each rule you break and each action you take!
It is important that you document your changes because doing so will compel you to think
about the consequences of what you are about to do and it provides a means of recording
the changes you make to the database structure. Should you decide later that the modific-
ations did not provide significant benefits, you can use the documentation as a guide to
reverse the modifications you initially made.
These are the items that you should record.
•
The reason you're breaking the rules:
Increasing processing performance and de-
creasing the time it takes to print complex reports are two of the most common
reasons for breaking the rules. Whatever your reason, be sure to state it thoroughly
and clearly.
•
The design principle you're violating:
Recording how you've altered the database
design will give you the means to reverse these changes later should you determine
that performance did not significantly improve. You might indicate that you're al-
tering the structure of a table, for example.
•
The aspect of the database that you're modifying:
Indicate which particular field,
table, relationship, or view you are going to alter. Once again, this information will
be valuable should you decide to reverse the modifications.
•
The specific modifications you are making:
Once you determine which item you
need to modify, record the
exact
modifications you make to that item. For ex-
ample, if you need to modify a relationship, note the exact changes you make to its
characteristics.
•
The anticipated effects on the database and the application program:
Any modi-
fications you make to the database are going to affect all accompanying end-user
application programs. For example, altering the structure of a particular table can
affect data integrity, view structures, data entry forms and reports built upon the
