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It guarantees that the spurious tuple generation does not occur with respect to relation schemas after decomposition.
The domain of attribute must include only atomic (simple, indivisible) values.
It is based on concept of full functional dependency. A functional dependency X --> Y is full functional dependency if removal of any attribute A from X means that the dependency does not hold any more.
A relation schema R is in 2NF if it is in 1NF and every non-prime attribute A in R is fully functionally dependent on primary key.
A relation schema R is in 3NF if it is in 2NF and for every FD X-->A either of the following is true
X is a Super-key of R.
A is a prime attribute of R.
In other words, if every non prime attribute is non-transitively dependent on primary key.
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