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Understanding Database Normalization: Key Concepts and Forms Explained

This chapter delves into the critical role of normalization in database design, focusing on various normal forms, including 1NF, 2NF, 3NF, BCNF, and 4NF. You will learn how to transform lower normal forms into higher ones, the importance of normalization in reducing data redundancy, and eliminating anomalies. The chapter also discusses situations where denormalization may be necessary for efficient information generation. Gain insight into the relationship between normalization and ER modeling, essential for creating effective database systems.

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Understanding Database Normalization: Key Concepts and Forms Explained

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  1. Chapter 4 Normalization of Database Tables Database Systems: Design, Implementation, and Management, Fifth Edition, Rob and Coronel

  2. In this chapter, you will learn: • What normalization is and what role it plays in database design • 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 E-R modeling are used concurrently to produce a good database design • That some situations require denormalization to generate information efficiently Database Systems: Design, Implementation, & Management, 5th Edition, Rob & Coronel

  3. Database Tables and Normalization • Table is basic building block in database design • Normalization is process for assigning attributes to entities • Reduces data redundancies • Helps eliminate data anomalies • Produces controlled redundancies to link tables • Normalization stages • 1NF - First normal form • 2NF - Second normal form • 3NF - Third normal form • 4NF - Fourth normal form Database Systems: Design, Implementation, & Management, 5th Edition, Rob & Coronel

  4. Need for Normalization Figure 4.1 Database Systems: Design, Implementation, & Management, 5th Edition, Rob & Coronel

  5. Figure 4.1 Observations • PRO_NUM intended to be primary key • Table entries invite data inconsistencies • Table displays data anomalies • Update • Modifying JOB_CLASS • Insertion • New employee must be assigned project • Deletion • If employee deleted, other vital data lost Database Systems: Design, Implementation, & Management, 5th Edition, Rob & Coronel

  6. Conversion to 1NF • Repeating groups must be eliminated • Proper primary key developed • Uniquely identifies attribute values (rows) • Combination of PROJ_NUM and EMP_NUM • Dependencies can be identified • Desirable dependencies based on primary key • Less desirable dependencies • Partial • based on part of composite primary key • Transitive • one nonprime attribute depends on another nonprime attribute Database Systems: Design, Implementation, & Management, 5th Edition, Rob & Coronel

  7. Dependency Diagram (1NF) Figure 4.4 Database Systems: Design, Implementation, & Management, 5th Edition, Rob & Coronel

  8. Data Organization: 1NF Figure 4.3 Database Systems: Design, Implementation, & Management, 5th Edition, Rob & Coronel

  9. 1NF Summarized • All key attributes defined • No repeating groups in table • All attributes dependent on primary key Database Systems: Design, Implementation, & Management, 5th Edition, Rob & Coronel

  10. Conversion to 2NF • Start with 1NF format: • Write each key component on separate line • Write original key on last line • Each component is new table • Write dependent attributes after each key PROJECT (PROJ_NUM, PROJ_NAME) EMPLOYEE (EMP_NUM, EMP_NAME, JOB_CLASS, CHG_HOUR) ASSIGN (PROJ_NUM, EMP_NUM, HOURS) Database Systems: Design, Implementation, & Management, 5th Edition, Rob & Coronel

  11. 2NF Conversion Results Figure 4.5 Database Systems: Design, Implementation, & Management, 5th Edition, Rob & Coronel

  12. 2NF Summarized • In 1NF • Includes no partial dependencies • No attribute dependent on a portion of primary key • Still possible to exhibit transitive dependency • Attributes may be functionally dependent on nonkey attributes Database Systems: Design, Implementation, & Management, 5th Edition, Rob & Coronel

  13. Conversion to 3NF • Create separate table(s) to eliminate transitive functional dependencies PROJECT (PROJ_NUM, PROJ_NAME) ASSIGN (PROJ_NUM, EMP_NUM, HOURS) EMPLOYEE (EMP_NUM, EMP_NAME, JOB_CLASS) JOB (JOB_CLASS, CHG_HOUR) Database Systems: Design, Implementation, & Management, 5th Edition, Rob & Coronel

  14. 3NF Summarized • In 2NF • Contains no transitive dependencies Database Systems: Design, Implementation, & Management, 5th Edition, Rob & Coronel

  15. Additional DB Enhancements Figure 4.6 Database Systems: Design, Implementation, & Management, 5th Edition, Rob & Coronel

  16. Boyce-Codd Normal Form (BCNF) • Every determinant in the table is a candidate key • Determinant is attribute whose value determines other values in row • 3NF table with one candidate key is already in BCNF Database Systems: Design, Implementation, & Management, 5th Edition, Rob & Coronel

  17. 3NF Table Not in BCNF Figure 4.7 Database Systems: Design, Implementation, & Management, 5th Edition, Rob & Coronel

  18. Decomposition of Table Structure to Meet BCNF Figure 4.8 Database Systems: Design, Implementation, & Management, 5th Edition, Rob & Coronel

  19. Decomposition into BCNF Figure 4.9 Database Systems: Design, Implementation, & Management, 5th Edition, Rob & Coronel

  20. Normalization and Database Design • Normalization should be part of the design process • E-R Diagram provides macro view • Normalization provides micro view of entities • Focuses on characteristics of specific entities • May yield additional entities • Difficult to separate normalization from E-R diagramming • Business rules must be determined Database Systems: Design, Implementation, & Management, 5th Edition, Rob & Coronel

  21. Initial ERD for Contracting Company Figure 4.10 Database Systems: Design, Implementation, & Management, 5th Edition, Rob & Coronel

  22. Modified ERD for Contracting Company Figure 4.11 Database Systems: Design, Implementation, & Management, 5th Edition, Rob & Coronel

  23. Final ERD for Contracting Company Figure 4.12 Database Systems: Design, Implementation, & Management, 5th Edition, Rob & Coronel

  24. Higher-Level Normal Forms • Fourth Normal Form (4NF) • Table is in 3NF • Has no multiple sets of multivalued dependencies Database Systems: Design, Implementation, & Management, 5th Edition, Rob & Coronel

  25. Conversion to 4NF Figure 4.15 Set of Tables in 4NF Figure 4.14 Multivalued Dependencies Database Systems: Design, Implementation, & Management, 5th Edition, Rob & Coronel

  26. Denormalization • Normalization is one of many database design goals • Normalized table requirements • Additional processing • Loss of system speed • Normalization purity is difficult to sustain due to conflict in: • Design efficiency • Information requirements • Processing Database Systems: Design, Implementation, & Management, 5th Edition, Rob & Coronel

  27. Unnormalized Table Defects • Data updates less efficient • Indexing more cumbersome • No simple strategies for creating views Database Systems: Design, Implementation, & Management, 5th Edition, Rob & Coronel

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