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Fig. 3.16 Network schema dependency relationship translation
due to a 1:1 relationship can be made in either direction). For a unary relationship,
the foreign key of 1:1 and a 1:n relationship can be mapped in the same or different
relation(s). For a unary m:n relationship, a relationship relation must be mapped
into the relational schema.
Substep 2—Map an n-ary relationship into relationship relation
An n-ary relationship has n + 1 possible varieties of connectivity: all n sides with
connected“1,”n−1sideswithconnected“1”andonesidewithconnectivity“n,”
n−2sideswithconnectivity“1”andtwosideswith“n,”andsoon,untilallsides
are “n.” As an example, consider a Collateral system where customers provide a
loan security for various loan contracts. Four of the possible ternary relationships
are illustrated in cases 1-4.
Case 1: Many customers may participate in any one collateral for many loan
contracts secured by many loan securities as shown in Fig. 3.18 .
Case 2: A customer may participate in any one collateral for one contract secured
by one loan security as shown in Fig. 3.19 .
Case 3: Many customers may participate in any one collateral for many loan
contracts secured by one loan security as shown in Fig. 3.20 .
Case 4: Many customers may participate in any one collateral for one loan con-
tract secured by one loan security as shown in Fig. 3.21 .
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