What is trivial functional dependency in dbms

What is trivial functional dependency in DBMS? / Define trivial functional dependency / What is the trivial property in normalization process?

Trivial Functional Dependency

A FD is said to be as Trivial, if it holds for all relations. In other words, a functional dependency A → B is said to be trivial, if B is the subset or equal to that of A. That is, if you know the value of B already, you would uniquely determine the value of B.

If all of the right hand side attributes are either subset or equal to the left hand side attributes in a functional dependency, then that particular functional dependency is said to be trivial.

For example, 

• A → A is trivial, 
• AB → B is trivial, 
• {regno, phone} → phone and so on.

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Describe trivial functional dependency in normalization process