TAILIEUCHUNG - Database Modeling & Design Fourth Edition- P25

Database Modeling & Design Fourth Edition- P25: Database technology has evolved rapidly in the three decades since the rise and eventual dominance of relational database systems. While many specialized database systems (object-oriented, spatial, multimedia, etc.) have found substantial user communities in the science and engineering fields, relational systems remain the dominant database technology for business enterprises. | Normalization This chapter focuses on the fundamentals of normal forms for relational databases and the database design step that normalizes the candidate tables step II d of the database design life cycle . It also investigates the equivalence between the conceptual data model . the ER model and normal forms for tables. As we go through the examples in this chapter it should become obvious that good thoughtful design of a conceptual model will result in databases that are either already normalized or can be easily normalized with minor changes. This truth illustrates the beauty of the conceptual modeling approach to database design in that the experienced relational database designer will develop a natural gravitation toward a normalized model from the beginning. For most database practitioners Sections through cover the critical normalization needed for everyday use through Boyce-Codd normal form BCNF . Section covers the higher normal forms of mostly theoretical interest however we do show the equivalency between higher normal forms and ternary relationships in the ER model and UML for the interested reader. Fundamentals of Normalization Relational database tables whether they are derived from ER or UML models sometimes suffer from some rather serious problems in terms of 107 108 CHAPTER 6 Normalization Sales product_name order_no cust_name cust_addr credit date sales_name vacuum cleaner 1458 Dave Bachmann Austin 6 1-3-03 Carl Bloch computer 2730 Qiang Zhu Plymouth 10 4-15-05 Ted Hanss refrigerator 2460 Mike Stolarchuck Ann Arbor 8 9-12-04 Dick Phillips DVD player 519 Peter Honeyman Detroit 3 12-5-04 Fred Remley radio 1986 Charles Antonelli Chicago 7 5-10-05 R. Metz CD player 1817 Ravishankar Mumbai 8 8-3-02 Paul Basile vacuum cleaner 1865 Charles Antonelli Chicago 7 10-1-04 Carl Bloch vacuum cleaner 1885 Betsy Karmeisool Detroit 8 4-19-99 Carl Bloch refrigerator 1943 Dave Bachmann Austin 6 1-4-04 Dick Phillips television 2315 Sakti .

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