1. Concepts of Database Management, Fifth Edition
Chapter 5:
Database Design 1:
Normalization

2. Objectives Discuss functional dependence Discuss primary keys
Define first normal form, second normal form, and third normal form
Describe the problems associated with tables (relations) that are not in first normal form, second normal form, or third normal form along with the mechanism for converting to all three
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3. Objectives
Discuss the problems associated with incorrect conversions to third normal form
Define fourth normal form
Describe the problems associated with tables (relations) that are not in fourth normal form and describe the mechanism for converting to fourth normal form
Understand how normalization is used in the database design process
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4. Normalization
Normalization process – enables you to identify the existence of potential problems, called updating anomalies, in the design of a relational database
Normal form – possesses a certain desirable collection of properties
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5. Figure 5.1: Premiere Products Data
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6. Functional Dependence
Column B is functionally dependent on Column A if A’s value determines a single value for B at a given time
Given A, a single value for B can be determined
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7. Functional Dependence
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8. Functional Dependence Example
Figures :
Functional Dependence Example
Rep Table Where LastName can determine record
Rep Table Where LastName cannot determine record
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9. Keys Column(s) C is primary key for table T if: Candidate Keys
Property 1: All columns in T are functionally dependent on C
Property 2: No subcollection of columns in C (assuming C is a collection of columns and not just a single column) also has Property 1
Candidate Keys
Column(s) on which all other columns in table are functionally dependent
Alternate Keys
Candidate keys not chosen as primary keys
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10. First Normal Form (1NF) Unnormalized table Table in 1NF
Contains a repeating group
Table in 1NF
Contains no repeating groups
Removal of repeating groups is starting point in quest for problem-free tables
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11. Figure 5.5: 1NF Example Unnormalized Table
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12. Figure 5.6: 1NF Example (con’t.)
Conversion to 1NF
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13. Second Normal Form (2NF)
1NF Tables may contain problems
Redundancy
Update Anomalies
Update, inconsistent data, additions, deletions
Occur because a column is dependent on a portion of a multi-column primary key
2NF Table
In 1NF and no nonkey column is dependent on only a portion of the primary key
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14. Figure 5.7: Second Normal Form
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15. Update Anomalies Update Inconsistent data Additions Deletions
Information is in multiple rows, difficult to update
Inconsistent data
Because of the duplication, a row that is not updated causes inconsistency
Additions
Dummy records are required to add new unused dependent rows
Deletions
Nonkey column (nonkey attribute) – when a column is not a part of the primary key
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16. Dependency Diagram
Dependency diagram – uses arrows to indicate all the functional dependencies present in a table
Partial dependencies – dependencies only on a portion of the primary key
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17. Dependency Diagram for Orders
Figure 5.8:
Dependency Diagram for Orders
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18. Third Normal Form (3NF) 2NF Tables may still contain problems
Redundancy and wasted space
Update Anomalies
Update, inconsistent data, additions, deletions
Occur because a column is dependent on a portion of a multi-column primary key
3NF Table
In 2NF and the only determinants contained are candidate keys
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19. Figure 5.9: 2NF Example
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20. Figure 5.10: Sample Customer Data
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21. Customers Dependency Diagram
Figure 5.11:
Customers Dependency Diagram
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22. Incorrect Decomposition
Decomposition must take place according to that described for 3NF
Even though you may decompose a table, you run the risk of splitting the functional dependence across different tables
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23. Figure 5.12:
3NF Example
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24. Figure 5.13: Incorrect Decomposition Example
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25. Fourth Normal Form (4NF)
3NF Tables may still contain problems
Dependencies
Update Anomalies
Update, additions, deletions
Occur because of multivalued dependencies
4NF Table
In 3NF and has no multivalued dependencies
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26. Figure 5.15: Incorrect 4NF Example
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27. Figure 5.16a:
4NF Example
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28. Figure 5.17: Normal Forms
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29. Summary
Normalization is a process of optimizing databases to prevent update anomalies
Normalization attempts to correct update issues by eliminating duplication
Duplication also creates inconsistency
Insertions can violate database integrity if the database is not normalized
Deletions can violate database integrity if the database is not normalized
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30. Summary (con’t.)
Normal Forms – First (1NF), Second (2NF), Third(3NF), and Fourth(4NF)
1NF has no repeating groups
2NF is in 1NF and no non-key column is dependent on only a portion of the primary key
3NF is in 2NF and the only determinants are candidate keys
4NF is in 3NF and has no multivalued dependencies
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