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6 Cards in this Set

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What is normalization?

Series of definitions for capturing common-sense relationships and removing redundancies.

What is First Normal form?

Values should be simple and flat (non-decomposable type, strings) and should contain atomic values only.

What is a functional dependency?

Functional dependencies capture the notion of something thing relating to one thing rather than many. i.e person has one date of birth.




Given a relation R attribute B of R is functionally dependent on attribute A of R.




A functionally determines B if each value of A has no more than one value of B.




(A and B can be composite.)

What is a trivial functional dependency?

A determines B holds in any relation Ri if B is a subset of A(composite).

What is a full functional dependency?

Attribute B of R is fully functionally dependant on attribute A of R is it is fully functionally dependent of A and NOT functionally dependent on any proper subset of A.




So if you take something away form A but it still functionally determines B then it is not full functional dependency.

What is second normal form?

A relation is in 2NF if it is in 1NF and every non-key attribute is fully functionally dependent on each candidate key.




To check if we are in 2NF: See if a non-key attribute is fully functionally dependent on the candidate key. i.e UKELECTORS is not fully functionally dependent on {UKNUM, PARTY}




If every non-key attribute is fully functionally dependant on each candidate key, we are in second normal form.