/    /  DBMS – Functional Dependency(2)

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.

ABCD
a1b1c1d1
a1b2c1d2
a2b2c2d2
a2b3c2d3
a3b3c2d4

 

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’.

 

Reference Links

Functional Dependency(2)