Ch 6 Flashcards
Normalization
A process for assigning attributes to entities
Unnormalized relation table
Stores redundant data
Can cause insertion, deletion, and modification anomalies
Normalization Theory
Provides a step by step method to remove redundant data an undesirable table structures
Prime attributes
Are the key attributes
Non-Prime attributes
nonKey Attributes
Normal Forms
Table are normalized by applying rules to create a series of normal forms
First Normal Form (1NF)
All underlying domains contain atomic values only
Intersection of each row and column contains one and only one value (no repeating groups)
Primary key is defined
Second Normal Form (2NF)
It is 1NF and every monkey attribute is fully dependent on the primary key, no partial dependency
Monkey attribute
One that is not a primary key or part of a primary key
Nonloss decomposition
No information is lost in the process of creating 2NF relations from a 1NF relation
Third Normal Form (3NF)
If it is 2NF and every monkey attribute is non transitively dependent on the primary key
Surrogate Keys (UID)
Doesn’t guarantee data integrity or unique values
Uses Indexes IF possible (refine Logic)
Boyce-Codd Normal Form (BCNF)
Every determinant is a candidate key
A special case of 3NF
The potential to violate BCNF may occur in a relation that:
Contains two (or more) composite candidate keys
These keys overlap and share at least one attribute
If a table contains only one candidate key or only non-composite keys, then
3NF and BCNF are equivalent
Fourth Normal Form (4NF)
It is in 3NF and has no multiple sets of multivalued dependencies
Denormalization
Normalized (decomposed) tables require additional processing, thus reducing system speed
