Database Reference
In-Depth Information
Figure 7.17. Identifying a multivalued field
So how would you resolve this multivalued field? Your first thought may be to create a
new field for each value, thus “flattening” the multivalued field into several single-valued
fields.
Figure 7.18
shows what will happen if you follow through with this idea.
Figure 7.18. The result of “flattening” the C
ATEGORIES
T
AUGHT
field
Unfortunately, this is not much of an improvement at all. There are three specific problems
that arise from this type of structure.
1.
Retrieving category information will be tedious at best.
A user attempting to find
all instructors who teach the WP category must be sure to search for this value
within each of the category fields—there is no guarantee that WP is consistently
stored in the same field. Failure to do so means that the user runs the risk of over-
looking a qualified instructor.
2.
There is no way for the RDBMS program to sort the category data in a meaningful
fashion.
