1 5 Concepts of Database Management, 4 th Edition, Pratt & Adamski Chapter 5 Database Design: Normalization

2 5 Concepts of Database Management, 4 th Edition, Pratt & Adamski Objectives  Discuss functional dependence  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

3 5 Concepts of Database Management, 4 th Edition, Pratt & Adamski 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

4 5 Concepts of Database Management, 4 th Edition, Pratt & Adamski 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

5 5 Concepts of Database Management, 4 th Edition, Pratt & Adamski Functional Dependence Example Rep Table Where LastName can determine record Rep Table Where LastName cannot determine record

6 5 Concepts of Database Management, 4 th Edition, Pratt & Adamski Keys  Column(s) C is primary key for table T if: 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

7 5 Concepts of Database Management, 4 th Edition, Pratt & Adamski First Normal Form (1NF)  Unnormalized table Contains a repeating group  Table in 1NF Contains no repeating groups  Removal of repeating groups is starting point in quest for problem-free tables

8 5 Concepts of Database Management, 4 th Edition, Pratt & Adamski 1NF Example Unnormalized Table

9 5 Concepts of Database Management, 4 th Edition, Pratt & Adamski 1NF Example (con’t.) Conversion to 1NF

10 5 Concepts of Database Management, 4 th Edition, Pratt & Adamski Second Normal Form (2NF)  1NF Tables may contain problems Redundancy Update Anomalies à Update, inconsistent data, additions, deletions à 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

11 5 Concepts of Database Management, 4 th Edition, Pratt & Adamski Dependency Diagram for Orders 2NF Example

12 5 Concepts of Database Management, 4 th Edition, Pratt & Adamski 2NF Example

13 5 Concepts of Database Management, 4 th Edition, Pratt & Adamski Third Normal Form (3NF)  2NF Tables may still contain problems Redundancy and wasted space Update Anomalies à Update, inconsistent data, additions, deletions à 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

14 5 Concepts of Database Management, 4 th Edition, Pratt & Adamski Customers Dependency Diagram

15 5 Concepts of Database Management, 4 th Edition, Pratt & Adamski 3NF Example

16 5 Concepts of Database Management, 4 th Edition, Pratt & Adamski 3NF Example

17 5 Concepts of Database Management, 4 th Edition, Pratt & Adamski Incorrect Decomposition Example

18 5 Concepts of Database Management, 4 th Edition, Pratt & Adamski Incorrect Decomposition Example

19 5 Concepts of Database Management, 4 th Edition, Pratt & Adamski 2nd Incorrect Decomposition Figure 5.14a

20 5 Concepts of Database Management, 4 th Edition, Pratt & Adamski 2nd Incorrect Decomposition

21 5 Concepts of Database Management, 4 th Edition, Pratt & Adamski Fourth Normal Form (4NF)  3NF Tables may still contain problems Dependencies Update Anomalies à Update, additions, deletions à Occur because of multivalued dependencies  4NF Table In 3NF and has no multivalued dependencies

22 5 Concepts of Database Management, 4 th Edition, Pratt & Adamski Incorrect 4NF Example

23 5 Concepts of Database Management, 4 th Edition, Pratt & Adamski 4NF Example

24 5 Concepts of Database Management, 4 th Edition, Pratt & Adamski Normal Forms