Entity Relationship Diagram - PowerPoint PPT Presentation

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Entity Relationship Diagram

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Entity Relationship Diagram ERD? 1976 Chen E-R ... – PowerPoint PPT presentation

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Title: Entity Relationship Diagram


1
Entity Relationship Diagram
2
ERD?
  • 1976 ? Chen ? ?? ??? E-R ??? ??? ???? ?? ?????
    ???? ?? ???? ? ??? ??? ?? ??? ??? ?? ???? ?? ????
    ??
  • ???? ?? ???, ???, ??????? ?? ??? ???? ?? ? ?? ???
    ??? ? ?? ???? ???
  • ?? ?? ??? ???? ? ?? ??? ??? ???? ?? ???? ?? ??
  • ?? ???? ???? ??????? ?? ??? ??? ????, ? ?? ?????
    ??, ??, ??? ???? ??

3
????
  • Entity
  • ??? ??? ??? ??? ??? ?? ?? ??? ???? ??(thing)
  • ??? ??
  • ??, ?? ?? ?? ?? ??? ?? ?
  • ??? ??
  • ?? ?? ?? ?? ??? ?, ?? ??? ???? ??
  • ?????? ???? ??? ??
  • Weak Entity
  • ? ??? ?? ?????? ???? ??
  • Weak entity? ??? ?? ?? ??? ?? ?? ?? ??

4
????(2)
  • Attribute
  • ??? ??? ???? ???? ??
  • Simple attribute
  • Composite attribute
  • ????? ???? ??? ????? ??

5
????(3)
  • Relationship
  • ??? ??? ???? ???? ??
  • Unary relationship
  • Binary relationship
  • Ternary relationship
  • ? ???? ???? ???? ?? ? ??? ??? ??? ??

6
????(4)
  • Connectivity
  • ? ??? ??? ??? ?? ??? ???? ???? ?
  • One to one
  • One to many
  • Many to many

7
????(5)
  • Cardinality
  • ??? ???? ??? ??? ?? ?? ????? ? ?? ??? ?????? ???

8
????
  • ERD ?? ??? ???? ??? ?? ???? ??? (??) ? ???? ??
    ???? ?? ? ??? ??? ?????? ????? ??? ??
  • ??? ?? ??, ??, ???? ??
  • ??? ???? ???? ??? ??, ??, ?? ?? ???? ?????? ??
    ERD ? ???? ??, ?? ???? ???? ?????? ?? ERD ?? ????
    ?? ???? ??
  • ???? ??? ????? ??? ?????? ? ??? ??

9
??
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