Relation Decomposition and Insufficiency of Normal Forms (cont.): 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 decomposition are needed to prevent from generating spurious tuples | Relational Database Design Algorithms and Further Dependencies 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 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 and ). DESIGNING A SET OF RELATIONS (2) Goals: Lossless join property (a must) – algorithm tests for general losslessness. Dependency preservation property – algorithms 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) 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. 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. Properties of Relational Decompositions (2) Relation Decomposition and Insufficiency of Normal Forms (cont.): 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. . | Relational Database Design Algorithms and Further Dependencies 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 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 and ). DESIGNING A SET OF RELATIONS (2) Goals: Lossless join property (a must) – algorithm tests for general losslessness. Dependency preservation property – algorithms decomposes a relation into BCNF components by .
