Database Reference
In-Depth Information
applying the three-step process you learned earlier, which yields the revised STUDENTS
tableandthenewSTUDENTINSTRUMENTStable.Whenyou'refinished,you'llbeable
to enter any number of instruments for a particular student. It will then be quite easy for
you to retrieve information such as the names of the students who have checked out a gui-
tar, a list of the instruments that are currently checked out by a particular student, and the
number of students who have checked out an electric piano.
Figure 7.25. Resolving a simple set of unnecessary duplicate fields
In some instances, a table can contain two or more
sets
of duplicate fields that represent
multiple occurrences of the same type of value.
Figure 7.26
shows a slightly different
version of the STUDENTS table shown in
Figure 7.24
; this version contains
two
sets of
duplicate fields. You may be thinking at this very moment, “Why is he saying there are
two
sets of duplicate fields when I clearly see
three?
” Contrary to what you may think,
I
NSTRUMENT
1/C
HECKOUT
D
ATE
1, for example, does not constitute a set of duplicate fields.
Quite the opposite—I
NSTRUMENT
1/I
NSTRUMENT
2/I
NSTRUMENT
3 constitute the first set of
