Functional Dependency(2)

 First Normal Form (1NF) :

 A relation is said to be in first normal form (1NF) if it contains all atomic values.

The below relation is in 1NF.

Partial Dependency  (PD) :

Let α → β  be an FD.

Let γ is a proper subset of α.   i.e.,  γ Ì α. And γ → β is also an FD.

Then,   α → β  is said to be  ‘Partial Dependency’. 

Here,  β is said to be ‘partially dependent’ on α.

Second Normal Form (2NF) :

A relation is said to be in second normal form (2NF) if it does not contain ‘partial dependency’.    

Example-1:   In the relation given above, it is known that

                                 A → C  and  AB → C                                 

             So,  AB → C is called ‘Partial Dependency’.

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Functional Dependency(2)