ch11-Relational Database Design Algorithms and Further Dependencies

Ch11-Relational Database Design Algorithms and Further Dependencies

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Slide 11- 1 Copyright © 2007 Ramez Elmasri and Shamkant B. Navathe
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Copyright © 2007 Ramez Elmasri and Shamkant B. Navathe Chapter 11 Relational Database Design Algorithms and Further Dependencies
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Slide 11- 3 Copyright © 2007 Ramez Elmasri and Shamkant B. Navathe Chapter Outline 0. Designing a Set of Relations 1. Properties of Relational Decompositions 2. Algorithms for Relational Database Schema 3. Multivalued Dependencies and Fourth Normal Form 4. Join Dependencies and Fifth Normal Form 5. Inclusion Dependencies 6. Other Dependencies and Normal Forms
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Slide 11- 4 Copyright © 2007 Ramez Elmasri and Shamkant B. Navathe DESIGNING A SET OF RELATIONS (1) The Approach of Relational Synthesis (Bottom-up Design): Assumes that all possible functional dependencies are known. First constructs a minimal set of FDs Then applies algorithms that construct a target set of 3NF or BCNF relations. Additional criteria may be needed to ensure the the set of relations in a relational database are satisfactory (see Algorithms 11.2 and 11.4).
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Slide 11- 5 Copyright © 2007 Ramez Elmasri and Shamkant B. Navathe DESIGNING A SET OF RELATIONS (2) Goals: Lossless join property (a must) Algorithm 11.1 tests for general losslessness. Dependency preservation property Algorithm 11.3 decomposes a relation into BCNF components by sacrificing the dependency preservation. Additional normal forms 4NF (based on multi-valued dependencies) 5NF (based on join dependencies)
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Slide 11- 6 Copyright © 2007 Ramez Elmasri and Shamkant B. Navathe 1. Properties of Relational Decompositions (1) Relation Decomposition and Insufficiency of Normal Forms: Universal Relation Schema: A relation schema R = {A1, A2, …, An} that includes all the attributes of the database. Universal relation assumption: Every attribute name is unique.
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Slide 11- 7 Copyright © 2007 Ramez Elmasri and Shamkant B. Navathe Properties of Relational Decompositions (2) Relation Decomposition and Insufficiency of Normal Forms (cont.): Decomposition: The process of decomposing the universal relation schema R into a set of relation schemas D = {R1,R2, …, Rm} that will become the relational database schema by using the functional dependencies. Attribute preservation condition: Each attribute in R will appear in at least one relation schema Ri in the decomposition so that no attributes are “lost”.
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Copyright © 2007 Ramez Elmasri and Shamkant B. Navathe Properties of Relational Decompositions (2) Another goal of decomposition is to have each individual relation Ri in the decomposition D be in BCNF or 3NF. Additional properties of decomposition
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Ch11-Relational Database Design Algorithms and Further Dependencies

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