X->Yis used to denote that when supplied values to the field(s) in set
X, the assigned value for each field in set
Ycan be determined. For example, if a database table is to contain fields for the social security number (
S), name (
N), address (
A), and phone (
P) and each person has been assigned a unique value for
Sfield functionally determines the
Pfields. This is written as
Develop a program that will identify each redundant FD in each input
group of FDs. An FD is redundant if it can be derived using other FDs
in the group. For example, if the group contains the FDs
A->C, then the
third FD is redundant since the field set
C can be
derived using the first two. (The
A fields determine
values for the
B fields, which in turn determine values
for the fields in
C.) In the group
B->A, all the FDs are redundant.
>. The lists of field names contain only uppercase alphabetic characters. Functional dependency lines contain no blanks or tabs. There are no trivially redundant FDs (for example,
A->A). For identification purposes, groups are numbered sequentially, starting with 1; the FDs are also numbered sequentially, starting with 1 in each group.
No redundant FDs.
3 A->BD BD->C A->C 6 P->RST VRT->SQP PS->T Q->TR QS->P SR->V 5 A->B A->C B->D C->D A->D 3 A->B B->C A->D 0
Set number 1 FD 3 is redundant using FDs: 1 2 Set number 2 FD 3 is redundant using FDs: 1 FD 5 is redundant using FDs: 4 6 2 Set number 3 FD 5 is redundant using FDs: 1 3 --OR-- FD 5 is redundant using FDs: 2 4 Set number 4 No redundant FDs.