Karteikarten
SCC 201 - Third Normal Form
Karten in diesem Stapel (9)
- 1A relational schema is said to be in 3rd normal form, if what?A relation schema R is in 3NF if every nonprime attribute of R meets both of the following conditions :
– It is fully functionally dependent on every key of R (it's in second normal form)
– It is non-transitively dependent on every key of R - 2A relational schema is said to be in 3rd normal form, if what in relation to super keys?A relational schema R is in 3NF if, whenever a functional dependency X --> A holds in R, either
– a) X is a superkey of R, or
– b) A is a prime attribute of R - 3A relational schema R is in BCNF if what?A relation schema R is in BCNF if, for every functional dependency X --> A, X is a superkey
This is same as 3NF except we drop test (b)
– (a) X is a superkey of R
– (b) A is a prime attribute of R - 4A relation schema R is in BCNF if what? Please use the term non-trivialA relation schema R is in BCNF if whenever
a non-trivial functional dependency X -> A holds in R, then X is a superkey of R - 5Describe trivial functional dependency using X -> Y>If an FD X → Y holds where Y subset of X, then it is called a trivial FD. Trivial FDs are always hold.
- 6Describe non-trivial functional dependency using x -> y?If an FD X → Y holds where Y is not subset of X, then it is called non-trivial FD.
- 7Describe completely non-trivial functional dependency using x -> Y?If an FD X → Y holds where x intersect Y = Φ, is said to be completely non-trivial FD.
- 8What are the two factors we have to consider when switching from 3NF to BCNF?– Keep dependency but also keep update problem, or
– Drop dependency and solve update problem - 9What factors do you have to consider when switching from 3NF to BCNF?– Keep dependency but also keep update problem, or
– Drop dependency and solve update problem
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- Karteikarten am SCC 201 - Third Normal Form, erstellt von Ayo Olutobi am 29/03/2017.
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- Ayo Olutobi
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