~ Leonardo da Vinci
Blog: http://rosinabignall.com
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Poor Normalization causes problems such as
A set of attributes
Definition
Definition
A set of ordered pairs <A,v>, one pair for each attribute in the heading
Definition
Essentially the implementation of a tuple
Definition
An ordered pair <H,h>, where h is the set of tuples all having heading H
Definition
Essentially the implementation of a relation
Definition
An expression of the form X->Y where X and Y are subsets of the attributes then whenever two tuples have the same value for X they also have the same value for Y
{ CITY } -> { STATUS}
All relations are by definition in 1NF
1NF simply means that each tuple in the relation contains exactly one value for each attribute
A relation is in second normal form (2NF) if and only if for every nontrivial FD X->Y at least one of the following is true: (a) X is a superkey; (b) Y is a subkey; (c)X is not a subkey.
No repeating groups
A relation is in third normal form (3NF) if and only if for every nontrivial FD X->Y either (a) X is a superkey; (b) Y is a subkey.
Every attribute must depend on the primary key
Every attribute must depend on the key, the whole key and nothing but the key
A relation is in Boyce/Codd normal form (BCNF) if and only if, for every nontrivial FD X->Y, X is a superkey.
1st Normal Form
2nd Normal Form
3rd Normal Form
Boyce/Codd Normal Form
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