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6 Cards in this Set
- Front
- Back
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What is normalization? |
Series of definitions for capturing common-sense relationships and removing redundancies. |
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What is First Normal form? |
Values should be simple and flat (non-decomposable type, strings) and should contain atomic values only. |
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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.) |
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What is a trivial functional dependency? |
A determines B holds in any relation Ri if B is a subset of A(composite). |
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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. |
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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. |
