Normalization

[jimin-kiim]

• Features of Good Relational Design
• Functional Dependencies
• Decomposition Using Functional Dependencies
• Normal Forms
• Functional Dependency Theory
• Algorithms for Decomposition using Functional Dependencies
• Decomposition Using Multivalued Dependencies
• More Normal Form
• Atomic Domains and First Normal Form
• Database-Design Process
• Modeling Temporal Data

[jimin-kiim]

Features of Good Relational Design

• no repetition in information
• need not to use null values
• lossless decomposition
• normalization theory .. based on
  • functional dependencies
  • multivalued dependencies

[jimin-kiim]

Functional Dependencies

• legal instance : an instance that satisfies all real world constraints
• legal instance of a database : one where all the relation instances are legal instances
• functional dependency
• closure of a set of functional dependencies : the set of all functional dependencies logically implied

Keys and Functional Dependencies

Trivial Functional Dependencies

ID, name -> ID
name -> name
In general, a -> b is trivial if b ⊆ a 

Lossless Decomposition

Dependency Preservation

• can check all the functional dependencies valid without joining

[jimin-kiim]

BCNF ( Boyce-Codd Normal Form)

• left side should be super key
• multiple composite candidate keys that overlap
• dependency preservation (?)
• lossless decomposition

[jimin-kiim]

3NF ( Third Normal Form )

• left side should be a superkey or right side is a prime attribute
• right side - left side should be a candidate key
• lossless decomposition
• dependency preservation
• disadvantage :
  • we may have to use null values to represent some of the possible meaningful relationships among data items
  • repetition of information