Ebook Modern database management (Twelfth edition): Part 2

Ebook Modern database management (Twelfth edition): Part 2 presents the following content: Physical Database Design and Performance; Database Application Development; Data Warehousing; Data Quality and Integration; Big Data and Analytics;...
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Ebook Modern database management (Twelfth edition): Part 2 Part III Database Design An Overview of Part Three Chapter 4 By the end of the database analysis phase of database development, systems and Logical Database database analysts have a fairly clear understanding of data storage and access Design and the requirements. However, the data model developed during analysis explicitly avoids Relational Model any ties to database technologies. Before we can implement a database, the conceptual data model must be mapped into a data model that is compatible with Chapter 5 the database management system to be used. Physical Database The activities of database design transform the requirements for data Design and Performance storage developed during database analysis into specifications to guide database implementation. There are two forms of specifications: 1. Logical specifications, which map the conceptual requirements into the data model associated with a ­ pecific database management system. s 2. Physical specifications, which indicate all the parameters for data stor- age that are then used as input for database implementation. During this phase, a database is actually defined using a data definition language. In Chapter 4 (“Logical Database Design and the Relational Model”), we describe logical database design, with special emphasis on the relational data model. Logical database design is the process of transforming the conceptual data model (described in Chapters 2 and 3) into a logical data model. Most database management systems in use today are based on the relational data model, so this data model is the basis for our discussion of logical database design. In Chapter 4, we first define the important terms and concepts for this model, including relation, primary key and surrogate primary key, foreign key, anomaly, normal form, normalization, functional dependency, partial functional dependency, and transitive dependency. We next describe and illustrate the process of transforming an E-R model to the relational model. Many modeling tools support this transformation; however, it is important that you understand the underlying principles and procedures. We then describe and illustrate in detail the important concepts of normalization (the process of designing well-structured relations). Appendix B, on the book’s Web site, includes further discussion of normalization. Finally, we describe how to merge relations from separate logical design activities (e.g., different groups within a large project team) while avoiding common pitfalls that may occur in this process. We end this discussion with a presentation of enterprise keys, which make relational keys distinct across relations. The purpose of physical database design, the topic of Chapter 5 (“Physical Database Design and Performance”), is to translate the logical description of data into the technical specifications for storing and retrieving data. The goal is to create a design for storing data that will provide adequate performance and ensure 190 Part III  •  Database Design database integrity, security, and recoverability. Physical database design produces the technical specifications that programmers and others involved in information systems construction will use during the implementation phase, which we discuss in Chapters 6 through 9. In Chapter 5, you will learn key terms and concepts for physical database design, including data type, page, pointer, denormalization, partitioning, indexed file organization, and hashed file organization. You will study the basic steps in developing an efficient physical database design. You will learn about choices for storing attribute values and how to select among these choices. You will also learn why normalized tables do not always form the best physical data files and how you can, if necessary, denormalize the data to achieve data retrieval speed improvements. You will learn about different file organizations and different types of indexes, which are important in speeding the retrieval of data. Appendix C, on the book’s Web site, addresses some additional constructs for physical data storage. In addition, you will learn how physical database design choices that improve data quality affect the process of validating the accuracy of financial reporting. These are essential issues today because of government regulations, such as Sarbanes- Oxley, and because of the growing realization that ensuring high data quality makes business sense. You must carefully perform physical database design because decisions made during this stage have a major impact on data accessibility, response times, security, user friendliness, information quality, and similarly important information system design factors. Database adm ...