Beginning Database Design- P14:This book focuses on the relational database model from a beginning perspective. The title is, therefore, Beginning Database Design. A database is a repository for data. In other words, you can store lots of information in a database. A relational database is a special type of database using structures called tables. Tables are linked together using what are called relationships. You can build tables with relationships between those tables, not only to organize your data, but also to allow later retrieval of information from the database | Planning and Preparation Through Analysis The business rules of a company when applied to a database model become that database model. The business rules are the tables relationships between those tables and even the constraint rules in addition to referential integrity constraints in a database. In fact the application of normalization to a set of initial company data tables is a more and more complex application of business rules to that company data environment. Normalization is the application of business rules. Figure 9-7 Iterative steps in the analysis methodology. Figure 9-8 shows some very simple example business rules. In Figure 9-8 there are many categories of instruments listed for auction. Each separate category of instruments such as brass instruments or the brass section has numerous instruments such as a trumpet trombone or sousaphone . One-to-many business rules brass_id category_id FK brass manufacturer in_stock Category category_id category stringed_id category_id FK stringed_instrument manufacturer in_stock number_of_strings woodwind_id category_id FK woodwind manufacturer in_stock used_or_new Each category has many subcategories in turn having many individual instruments Percussion percussion_id category_id FK percussion manufacturer in_stock free_snare_drum Figure 9-8 A one-to-many relationship is a business rule. 233 Chapter 9 In Figure 9-8 the very act of separating each of multiple instrument sections into separate tables is a very simplistic form of creating business rule representations using tables and the relationships between them. The ERD in Figure 9-8 is not standard normalization but is shown to demonstrate clearly how the relationships created between different tables actually create the business rules or operational functionality of a company. In this case the company is the online auction company that allows auction listings for sales of musical instruments for sale at auctions online. Auction House Categories Figure 9-9 shows a .
