Schema Refinement and Normalization

22/01/99


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Sommario

Schema Refinement and Normalization

The Evils of Redundancy

Functional Dependencies (FDs)

Example: Constraints on Entity Set

Example (Contd.)

Refining an ER Diagram

Reasoning About FDs

Reasoning About FDs (Contd.)

Reasoning About FDs (Contd.)

Normal Forms

Boyce-Codd Normal Form (BCNF)

Third Normal Form (3NF)

What Does 3NF Achieve?

Decomposition of a Relation Scheme

Example Decomposition

Problems with Decompositions

Lossless Join Decompositions

More on Lossless Join

Dependency Preserving Decomposition

Dependency Preserving Decompositions (Contd.)

Decomposition into BCNF

BCNF and Dependency Preservation

Decomposition into 3NF

Minimal Cover for a Set of FDs

Summary of Schema Refinement

Autore:Raghu Ramakrishnan