Chapter%2005a - 5 Chapter 5, part 1 Normalization of...

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5 1 Chapter 5, part 1 Normalization of Database Tables Database Systems: Design, Implementation, and Management, Seventh Edition, Rob and Coronel
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th 5 2 In this chapter, you will learn: What normalization is and what role it plays in the database design process About the normal forms 1NF, 2NF, 3NF, BCNF, and 4NF How normal forms can be transformed from lower normal forms to higher normal forms That normalization and ER modeling are used concurrently to produce a good database design That some situations require denormalization to generate information efficiently
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th 5 3 Database Tables and Normalization Normalization Process for evaluating and correcting table structures to minimize data redundancies Reduces data anomalies Works through a series of stages called normal forms: First normal form (1NF) Second normal form (2NF) Third normal form (3NF)
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th 5 4 Database Tables and Normalization (continued) Normalization (continued) 2NF is better than 1NF; 3NF is better than 2NF For most business database design purposes, 3NF is as high as we need to go in normalization process Highest level of normalization is not always most desirable
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th 5 5 The Need for Normalization Example: Company that manages building projects Charges its clients by billing hours spent on each contract Hourly billing rate is dependent on employee’s position Periodically, report is generated that contains information displayed in Table 5.1
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th 5 6 The Need for Normalization (continued)
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th 5 7 The Need for Normalization (continued)
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th 5 8 The Need for Normalization (continued) Structure of data set in Figure 5.1 does not handle data very well The table structure appears to work; report generated with ease Unfortunately, report may yield different results depending on what data anomaly has occurred
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th 5 9 The Normalization Process Each table represents a single subject No data item will be unnecessarily stored in more than one table All attributes in a table are dependent on the primary key
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th 5 10 The Normalization Process (continued)
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Chapter%2005a - 5 Chapter 5, part 1 Normalization of...

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