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
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Autore:Raghu Ramakrishnan
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