Flashcards in Function Dependencies & Normalization Deck (19):
Types of update anomalies
Insertion, Deletion, Modification
Given X->Y, the attributes X will determine the attributes Y uniquely.
Y is functionally dependent on X
X functionally determines Y
Full functional dependencies
Given X->Y, there can be no attributes taken out of X such that X can still determine Y
All domain values in R are atomic.
In other words, no nested values, lists of attributes etc.
R is in 1NF AND every non-key attribute if fully dependent on the primary key.
In other words, each non-candidate key needs to be only identified by the entire primary key, not just part of it.
R is in 2NF AND every non-key attribute is non-transitively dependent on the primary key.
In other words, there are not any attributes that depend on the status of other non-prime attributes
Boyce-Codd Normal Form:
Every functional dependency of the relation, R, is determined by primary key(s) only.
Attributes that uniquely identity a tuple
A minimal superkey
A key that could uniquely identity a relation
A secondary key that could have been the primary key
A key that maps to another entity
Keys that exist in the real world, ssn,
Keys with two or more attributes
Key with no real world meaning, opposite of a natural key
Surrogate Key VS Natural Key
When choosing a Primary Key it is best to use a natural key.
When a relation is decomposed, can it be composed again without loss of any data.
When a relation has multi-valued dependancies