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Database System: Chapter 8 - Normalization for Relational Databases includes Normal Forms Based on Primary Keys (Normalization of Relations, Practical Use of Normal Forms, Definitions of Keys and Attributes Participating in Keys,.), General Normal Form Definitions (For Multiple Keys), BCNF (Boyce-Codd Normal Form). | Chapter 8 Normalization for Relational Databases Copyright © 2004 Pearson Education, Inc. 5/14/2020 4:10:15 AM Outline Normal Forms Based on Primary Keys Normalization of Relations Practical Use of Normal Forms Definitions of Keys and Attributes Participating in Keys First Normal Form Second Normal Form Third Normal Form General Normal Form Definitions (For Multiple Keys) BCNF (Boyce-Codd Normal Form) Slide 8 - Normalization of Relations (1) Normalization: The process of decomposing unsatisfactory "bad" relations by breaking up their attributes into smaller relations Normal form: Condition using keys and FDs of a relation to certify whether a relation schema is in a particular normal form Slide 8 - Normalization of Relations (2) 2NF, 3NF, BCNF based on keys and FDs of a relation schema 4NF based on keys, multi-valued dependencies : MVDs; 5NF based on keys, join dependencies : JDs (Chapter 11) Additional properties may be needed to ensure a good relational design . | Chapter 8 Normalization for Relational Databases Copyright © 2004 Pearson Education, Inc. 5/14/2020 5:23:41 AM Outline Normal Forms Based on Primary Keys Normalization of Relations Practical Use of Normal Forms Definitions of Keys and Attributes Participating in Keys First Normal Form Second Normal Form Third Normal Form General Normal Form Definitions (For Multiple Keys) BCNF (Boyce-Codd Normal Form) Slide 8 - Normalization of Relations (1) Normalization: The process of decomposing unsatisfactory "bad" relations by breaking up their attributes into smaller relations Normal form: Condition using keys and FDs of a relation to certify whether a relation schema is in a particular normal form Slide 8 - Normalization of Relations (2) 2NF, 3NF, BCNF based on keys and FDs of a relation schema 4NF based on keys, multi-valued dependencies : MVDs; 5NF based on keys, join dependencies : JDs (Chapter 11) Additional properties may be needed to ensure a good relational design (lossless join, dependency preservation; Chapter 11) Slide 8 - Practical Use of Normal Forms Normalization is carried out in practice so that the resulting designs are of high quality and meet the desirable properties The practical utility of these normal forms becomes questionable when the constraints on which they are based are hard to understand or to detect The database designers need not normalize to the highest possible normal form. (usually up to 3NF, BCNF or 4NF) Denormalization: the process of storing the join of higher normal form relations as a base relation—which is in a lower normal form Slide 8 - Definitions of Keys and Attributes Participating in Keys (1) A superkey of a relation schema R = {A1, A2, , An} is a set of attributes S subset-of R with the property that no two tuples t1 and t2 in any legal relation state r of R will have t1[S] = t2[S] A key K is a superkey with the additional property that removal of any attribute from K will cause K not to be a superkey .
