Chapter10

Chapter10 - Copyright 2007 Ramez Elmasri and Shamkant B....

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Slide 10- 1 Copyright © 2007 Ramez Elmasri and Shamkant B. Navathe
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Copyright © 2007 Ramez Elmasri and Shamkant B. Navathe Chapter 10 Functional Dependencies and Normalization for Relational Databases
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Slide 10- 3 Copyright © 2007 Ramez Elmasri and Shamkant B. Navathe Chapter Outline 1 Informal Design Guidelines for Relational Databases 1.1Semantics of the Relation Attributes 1.2 Redundant Information in Tuples and Update Anomalies 1.3 Null Values in Tuples 1.4 Spurious Tuples 2 Functional Dependencies (FDs) 2.1 Definition of FD 2.2 Inference Rules for FDs 2.3 Equivalence of Sets of FDs 2.4 Minimal Sets of FDs
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Slide 10- 4 Copyright © 2007 Ramez Elmasri and Shamkant B. Navathe Chapter Outline 3 Normal Forms Based on Primary Keys 3.1 Normalization of Relations 3.2 Practical Use of Normal Forms 3.3 Definitions of Keys and Attributes Participating in Keys 3.4 First Normal Form 3.5 Second Normal Form 3.6 Third Normal Form 4 General Normal Form Definitions (For Multiple Keys) 5 BCNF (Boyce-Codd Normal Form)
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Slide 10- 5 Copyright © 2007 Ramez Elmasri and Shamkant B. Navathe 1 Informal Design Guidelines for Relational Databases (1) What is relational database design? The grouping of attributes to form "good" relation schemas Two levels of relation schemas The logical "user view" level The storage "base relation" level Design is concerned mainly with base relations What are the criteria for "good" base relations?
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Slide 10- 6 Copyright © 2007 Ramez Elmasri and Shamkant B. Navathe Informal Design Guidelines for Relational Databases (2) We first discuss informal guidelines for good relational design Then we discuss formal concepts of functional dependencies and normal forms - 1NF (First Normal Form) - 2NF (Second Normal Form) - 3NF (Third Normal Form) - BCNF (Boyce-Codd Normal Form) Additional types of dependencies, further normal forms, relational design algorithms by synthesis are discussed in Chapter 11
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Slide 10- 7 Copyright © 2007 Ramez Elmasri and Shamkant B. Navathe 1.1 Semantics of the Relation Attributes GUIDELINE 1: Informally, each tuple in a relation should represent one entity or relationship instance. (Applies to individual relations and their attributes). Attributes of different entities (EMPLOYEEs, DEPARTMENTs, PROJECTs) should not be mixed in the same relation Only foreign keys should be used to refer to other entities Entity and relationship attributes should be kept apart as much as possible. Bottom Line: Design a schema that can be explained easily relation by relation. The semantics of attributes should be easy to interpret.
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Slide 10- 8 Copyright © 2007 Ramez Elmasri and Shamkant B. Navathe Figure 10.1 A simplified COMPANY relational database schema
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Slide 10- 9 Copyright © 2007 Ramez Elmasri and Shamkant B. Navathe 1.2 Redundant Information in Tuples and Update Anomalies Information is stored redundantly
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Chapter10 - Copyright 2007 Ramez Elmasri and Shamkant B....

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