Database Reference
In-Depth Information
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There is a meaningful limit to the number of records that can be interrelated with-
in the relationship.
You implemented this by designating the appropriate degree of
participation for each table (or key field) within the relationship.
As you know, relationship-level integrity is the third component of overall data integrity.
(The first is table-level integrity and the second is field-level integrity.)You'll establish the
final component of overall data integrity in the next chapter when you learn how to estab-
lish business rules for the database.
Case Study
It's now time to identify the relationships that exist for the tables that appear on the final
table list for Mike's Bikes. You've assigned your assistant, Zachary, to this part of the
design process, and he's currently working with these tables:
CUSTOMERS
EMPLOYEES
INVOICES
PRODUCTS
VENDORS
Zachary's first order of business is to identify the relationships that currently exist between
thetables.HedecidestomeetonlywithMikebecausetherearefewtablesinthisdatabase,
and he figures that Mike should be familiar enough with the tables to help him verify the
relationships.
Before Zachary meets with Mike, he creates a table matrix and identifies as many relation-
ships as possible.
Figure 10.65
shows his completed matrix.
Figure 10.65. Identifying the relationships among the tables in the Mike's Bikes data-
base