Database Reference
In-Depth Information
duplicatefields,andC
HECKOUT
D
ATE
1/C
HECKOUT
D
ATE
2/C
HECKOUT
D
ATE
3constitutethe
second set of duplicate fields.
Figure 7.26. Example of a table with multiple sets of duplicate fields
You've probably realized that these two sets of duplicate fields are actually two flattened
multivalued fields and that you can resolve them in the same manner as in the previous
example. The only other issue that you must be concerned with is the distinct one-to-one
association between an instrument and a checkout date. This won't be a problem, however,
because you've dealt with this type of scenario before. If you visualize one multivalued
field called I
NSTRUMENTS
and another called C
HECKOUT
D
ATE
, you'll see that the overall
tablestructureisquitesimilar totheonein
Figure7.21
.
(Inthatfigure,there'saone-to-one
association between the C
ATEGORIES
T
AUGHT
and M
AXIMUM
L
EVEL
T
AUGHT
fields.)
Figure 7.27
illustrates how you can fix this table. As before, the shaded version of the
STUDENTS table shows how you visualize the instrument and checkout date fields as sin-
gularmultivalued fields.Youthenresolvethemultivalued fieldsbyapplyingthethree-step
processyoulearnedearlier,yieldingtherevisedSTUDENTStableandthenewSTUDENT
INSTRUMENTS table.
