tailieunhanh - Lecture Fundamentals of database systems: Chapter 11 - Emasri, Navathe

Chapter 11 present the contents: Designing a set of relations, properties of relational decompositions, algorithms for relational database schema, multivalued dependencies and fourth normal form, join dependencies and fifth normal form, inclusion dependencies, other dependencies and normal forms. | 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 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 and . Copyright 2007 Ramez Elmasri and Shamkant B. Navathe lide 11-3 Copyright 2007 Ramez Elmasri and Shamkant B. Navathe lide 11-4 Lossless join property a must Algorithm tests for general losslessness. Dependency preservation property Algorithm 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 Copyright 2007 Ramez Elmasri and Shamkant B. Navathe lide 11 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. Copyright 2007 Ramez Elmasri and Shamkant B. Navathe Slide 11-6 1 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 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 . Another goal of decomposition is to have each individual relation Ri in the decomposition D be in BCNF or 3NF. Additional properties of .