 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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 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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 Normalization process – enables you to identify the existence of potential problems, called updating anomalies, in the design of a relational database
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 Normal form – possesses a certain desirable collection of properties
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Figure 5.1:
Premiere Products Data
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 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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Figures 5.3-5.4:
Functional Dependence Example
Rep Table Where LastName can determine record
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Rep Table Where LastName cannot determine record
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 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
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 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
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Figure 5.5: 1NF Example
Unnormalized Table
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Figure 5.6: 1NF Example (con’t.)
Conversion to 1NF
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 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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Figure 5.7:
Second Normal Form
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 Update
 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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 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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Figure 5.8:
Dependency Diagram for Orders
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 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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Figure
5.9: 2NF
Example
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Figure 5.10: Sample Customer Data
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Figure 5.11:
Customers Dependency Diagram
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 Decomposition must take place according to that described for 3NF
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 Even though you may decompose a table, you run the risk of splitting the functional dependence across different tables
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Figure 5.12:
3NF Example
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Figure 5.13:
Incorrect
Decomposition
Example
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 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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Figure 5.15:
Incorrect
4NF Example
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Figure 5.16a:
4NF Example
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Figure 5.17: Normal Forms
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 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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 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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