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Chapter 5The Relational Model and
Normalization
David M. Kroenke
Database Processing
© 2000 Prentice Hall
Chapter 5
© 2000 Prentice Hall
The Relational Model
• Broad, flexible model• Basis for almost all DBMS products• E.F. Codd defined well-structured
“normal forms” of relations, “normalization”
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Chapter 5
© 2000 Prentice Hall
Relation
• Two-dimensional table• Rows are tuples• Columns are attributes
Page 113
Equivalent Relational Terms
Page 114Figure 5-1 © 2000 Prentice Hall
Functional Dependency“relationship between or among
attributes”
Page 114Figure 5-2 © 2000 Prentice Hall
Chapter 5
© 2000 Prentice Hall
Functional Dependency Notation
SID MajorComputerSerialNumber
MemorySize
(SID, ClassName) Grade
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Key“a group of one or more attributes
that uniquely identifies a row”
Page 116Figure 5-3 © 2000 Prentice Hall
Combination Key
Page 117Figure 5-4 © 2000 Prentice Hall
Chapter 5
© 2000 Prentice Hall
Normalization
“the process of evaluating and converting a relation to reduce modification anomalies”
Page 118
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Anomaly
“an undesirable consequence of data modification in which two or more different themes are entered (insertion anomaly) in a single row or two or more themes are lost if the row is deleted (deletion anomaly)”
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Normal Forms
“classes of relations and techniques for preventing anomalies”
DK/NF = Domain Key Normal Form(free of modification anomalies)
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First Normal Form“any table of data that meets the
definition of a relation”
Figure 5-3 © 2000 Prentice Hall
Second Normal Form“when all of a relation’s nonkey attributes
are dependent on all of the key”
Figure 5-5 © 2000 Prentice Hall
Third Normal Form“if it is in second normal form and
has no transitive dependencies”
Figure 5-7 © 2000 Prentice Hall
Boyce-Codd Normal Form
“if every determinant is a candidate key”
Figure 5-8 © 2000 Prentice Hall
Fourth Normal Form“if in BCNF and has no multi-value
dependencies”
Figure 5-11 © 2000 Prentice Hall
Chapter 5
© 2000 Prentice Hall
Fifth Normal Form
? Page 125
Chapter 5
© 2000 Prentice Hall
Domain Key Normal Form
“if every constraint on the relation is a logical consequence of the definition of keys and domains”
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© 2000 Prentice Hall
DK/NF Terms
• Constraint “a rule governing static values of attributes”
• Key “unique identifier of a tuple”• Domain “description of an
attribute’s allowed values”
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DK/NF Example
Figure 5-13 © 2000 Prentice Hall
DK/NF Example
Figure 5-15 © 2000 Prentice Hall
DK/NF Example
Figure 5-16 © 2000 Prentice Hall
Summary of Normal Forms
Figure 5-18 © 2000 Prentice Hall
Chapter 5
© 2000 Prentice Hall
A B relationships
A B and B A one-to-oneA B but B not A many-to-oneA not B and B not A many-to-many
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Summary of Relationships
Figure 5-19 © 2000 Prentice Hall
Chapter 5
© 2000 Prentice Hall
Optimization
• De-Normalization• Controlled Redundancy
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