Transcript Chapter 6: Database Design Using Entity

Database Processing
Chapter 6
Database Design Using
Entity-Relationship Models
David M. Kroenke
© 2000 Prentice Hall
Chapter 6
Entities & Relationships
“those things that users want to track”
“how entities relate to one another”
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Representation of an Entity
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Figure 6-1
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Customer Entity in DK/NF
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Figure 6-2
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Normalized Entity
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Figures 6-3a and 6-3c
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Chapter 6
Has-A Relationships
• 1:1 or 1:N
• Foreign key
“when the key of one relation is stored
in a second relation”
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1:1 Relationships
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Figure 6-6
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1:N Relationships
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Figure 6-8
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Chapter 6
1:N Relationship Terms
• Parent
“on the one side of the relationship”
• Child
“on the many side of the relationship
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1:N Data Structure Diagram
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Figure 6-9
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N:M Relationships
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Figure 6-13
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Chapter 6
Other Relationships
• Recursive
“relationship among entities of the
same class”
• Ternary
• IS-A
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E-R Diagram
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Figure 6-20a
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Relations for E-R Diagram
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Figure 6-20b
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Chapter 6
Patterns of Relationships
• Tree
• Simple Networks
• Bills of Materials
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Chapter 6
Tree
“hierarchy; a data structure in which
the elements of the structure have
only one-to-many relationships with
one another”
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Tree E-R diagram
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Figure 6-22
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Chapter 6
Simple Network
“data structure having only 1:N
relationships, but the elements may
have more than one parent as long as
the parents are of different types”
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Simple Network E-R Diagram
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Figure 6-24
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Complex Network
“a data structure of elements in which at
least one of the relationships is N:M”
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Figure 6-25
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Bills of Materials
“a special data structure that occurs
frequently in manufacturing
applications”
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Figure 6-26
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