Chapter 5: The Relational Model and Normalization

Report
Database Processing
Chapter 5
The Relational Model and
Normalization
David M. Kroenke
© 2000 Prentice Hall
Chapter 5
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
Relation
• Two-dimensional table
• Rows are tuples
• Columns are attributes
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Equivalent Relational Terms
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Figure 5-1
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Functional Dependency
“relationship between or among
attributes”
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Figure 5-2
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Chapter 5
Functional Dependency
Notation
SID  Major
ComputerSerialNumber  MemorySize
(SID, ClassName)  Grade
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Key
“a group of one or more attributes that
uniquely identifies a row”
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Figure 5-3
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Combination Key
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Figure 5-4
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Chapter 5
Normalization
“the process of evaluating and
converting a relation to reduce
modification anomalies”
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Chapter 5
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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Chapter 5
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
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Second Normal Form
“when all of a relation’s nonkey attributes
are dependent on all of the key”
Figure 5-5
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Third Normal Form
“if it is in second normal form and has
no transitive dependencies”
Figure 5-7
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Boyce-Codd Normal Form
“if every determinant is a candidate key”
Figure 5-8
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Fourth Normal Form
“if in BCNF and has no multi-value
dependencies”
Figure 5-11
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Chapter 5
Fifth Normal Form
?
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Chapter 5
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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Chapter 5
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
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DK/NF Example
Figure 5-15
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DK/NF Example
Figure 5-16
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Summary of Normal Forms
Figure 5-18
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Chapter 5
A  B relationships
A  B and B  A
A  B but B not  A
A not  B and B not  A
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one-to-one
many-to-one
many-to-many
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Summary of Relationships
Figure 5-19
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Chapter 5
Optimization
• De-Normalization
• Controlled Redundancy
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