Web design - this business rules. It is generally common knowledge
this business rules. It is generally common knowledge that some business rule implementation is often most effectively divided up between database and applications. DKNF is an ideal form and an ultimate or final form of relational database normalization. This level of normalization is more mathematically perfect and has beauty in its granular simplicity. In an object database model, this approach is perfectly suited where individual data items are only ever accessed as unique elements (primary keys) and records are never accessed in groups. In a relational database model where commercially most databases require not only exact matches but also range searching for reporting, this level of intensity in normalization nearly always has a seriously negative impact on general database and application performance, and thus a negative effect on end-user satisfaction. End-user satisfaction is the objective of any application. If it isn t, it should be because they usually pay the bills! Summary In this chapter, you learned about: . What normalization is, its benefits and potential hazards . A layman s method of understanding normalization . A purist, academic definition of normalization . How referential integrity is maintained using primary and foreign keys . Normal Forms from 1st through to 5th, including Boyce-Codd Normal Form and Domain Key Normal Form . Special terminology used in Normal Forms The next chapter discusses some advanced relational database modeling techniques, including denormalization, special tricks used for different database model types, followed by introductions to the object database model and data warehouse database modeling. Exercises 1. Write five CREATE TABLE commands for the tables in Figure 4-29. Ensure that all primary key, foreign key, and any potentially necessary unique keys are included. 2. Write CREATE INDEX commands to create all indexes on any foreign keys indicated in the CREATE TABLE commands written for the previous question. 122 Chapter 4
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