What is Functional dependency

Question

Hi!!

I am new to database, can someone explain to me what is a functional dependency.

Thanks!

Answer 1

A relation is said to be in Functional dependency when one attribute uniquely defines another attribute.

For Example, R is a Relation, X and Y are two attributes. T1 and T2 are two tuples.

 Then,

T1[X]=T2[X] and T1[Y]=T2[Y] means the value of component X uniquely define the value of component Y.

Also, X->Y means Y is functionally dependent on X.