Database Reference
In-Depth Information
1.
Remove the field from the table and use it as the basis for a new table. If neces-
sary, rename the field in accordance with the field naming guidelines that you
learned earlier in this chapter.
2.
Use a field (or set of fields) from the
original
table to relate the original table to
the new table; try to select fields that represent the subject of the table as closely as
possible. The field(s) you choose will appear in both tables.
3.
Assign an appropriate name, type, and description to the new table and add it to
the final table list.
You used this procedure to resolve a multivalued field called C
ATEGORIES
T
AUGHT
in an
INSTRUCTORS table.
Figure 10.38
shows the original version of the table and the results
of applying the procedure.
Figure 10.38. The original resolution of the C
ATEGORIES
T
AUGHT
multivalued field
There's one final fact about a multivalued field that you need to learn: An inherent one-to-
manyrelationshipexistsbetweenagivensetofvalueswithinamultivaluedfieldandthere-
cord in which they reside. You'll see this when you examine the original INSTRUCTORS
table in
Figure 10.38
.
A single instructor (such as Kira Bently) can teach one or more cat-
egories (DTP, SS, WP)—this holds true for every record in the table.
When you properly resolve the multivalued field, the tables produced by the procedure in-
herit the relationship. This is clearly the case with the revised INSTRUCTORS and new
INSTRUCTOR CATEGORIES tables. You can now establish this one-to-many relation-
