Full functional dependency(FFD)

The term full functional dependency (FFD) is used to indicate the minimum set of attributes in of a functional dependency (FD). In other words, the set of attributes X will be fufunctionally dependent on the set of attributes Y if the following conditions are satisfied: 

• X is functionally dependent on Y and
• X is not functionally dependent on any subset of Y.

 In relation ASSIGN of table  it is true that
FD: {EMP-ID,PROJECT, PROJECT-BUDGET}  -> {YRS-SPENT-BY-EMP-ON PROJECT}

 The values of EMP-ID, PROJECT and PROJECT-BUDGET determine a unique value of YRS-SPENT-BY-EMP-ON-PROJECT. However, it is not a full functional dependency because neither the EMP-ID -> YRS-SPENT-BY-EMP-ON-PROJECT nor the PROJECT -> YRS-SPENT-BY-EMP-ON-PROJECT holds true.
In fact, it is sufficient to know only the value of a subset of {EMP-ID, PROJECT, PROJECTBUDGET), namely, {EMP-ID, PROJECT}, to determine the YRS-SPENT-BY-EMP-ON PROJECT.  Thus, the correct full functional dependency (FFD) can be written as:
 FD: {EMP-ID,PROJECT} -> {YRS-SPENT-BY-EMP-ON-PROJECT}

 

Relation R1:BUDGET
PROJECT	PROJECT-BUDGET
P1	INR 100 CR
P2	INR 150 CR
P3	INR 200 CR
P4	INR 100 CR
P5	INR 150 CR
P6	INR 300 CR

 

Relation R2:ASSIGN
EMP-NO	PROJECT	YRS-SPENT-BY- EMP-ON-PROJECT
106519	P1	5
112233	P3	2
106519	P2	5
123243	P4	10
106519	P3	3
111222	P1	4

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