Database Reference
In-Depth Information
instead address and establish the constraint
outside
of the logical design of the database.
How do you determine whether you can properly represent a given constraint within this
process? You do so by identifying the
type
of business rule you're defining.
Types of Business Rules
There are two major types of business rules:
database oriented
and
application oriented.
Bothtypesofbusinessrulesimposesomeformofconstraintandhelpenforceandmaintain
overall data integrity, but they differ with regard to where and how they are established.
Database-oriented
business rules impose constraints that you can establish within the
lo-
gical
design of the database. You implement a given constraint by modifying various field
specification elements, relationship characteristics, or a combination of the two. The state-
ment from which you derive the constraint is a database-oriented business rule if you can
meaningfully
and
clearly
establish the constraint by either of these means. For example,
say you have a VENDORS table and define the following business rule for the V
END
S
TATE
field in that table:
We conduct business exclusively with vendors from the Pacific
Northwest.
ThisbusinessrulelimitsthevaluesthatyoucanenterintotheV
END
S
TATE
fieldtoWA,OR,
ID, and MT. You can establish the business rule's constraint in a meaningful manner by
modifying the Range of Values element in the field specifications for the V
END
S
TATE
field.
Figure 11.2
shows the modification.
