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System models

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3-1 * entity relationship ERD ... – PowerPoint PPT presentation

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Title: System models


1
??3????3-1?????
2
Entity-Relationship Model,( E/R Model)
  • ??????(Entity-Relationship Model)
  • ????????????????????????????,???????(Entity-Relati
    onship Diagram)????????

3
ERD ????
  • ERD?????????

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?????
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4
Entity and Attribute
5
?????(entity integrity)
  • ??????????????,??primary key(??)????null??
  • ?????????????,????????????

6
ERD Weak Entity
  • ?????ER Model??????????,?????????????????????????
    ?????

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1
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N
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7
Implement ER Model (cont.)
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8
Implement ER Model (cont..)
9
Implement ER Model (cont...)
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10
Relationship
1
1
n
1
n
m
11
1 ? 1 ??
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A B C D E . . . .
D1 D2 D3 D4 D5 D6 D7 D8 D9 . . .
R1 R2 R3 R4 R5 R6 R7 . . .
12
1 ? 1 (cont.)
??
1
1
??(???)
??
13
1 ? ? ??
??
??
??
A B C D E . . . .
D1 D2 D3 D4 D5 D6 D7 D8 D9 . . .
R1 R2 R3 R4 R5 R6 R7 . . .
14
1 ? ? (cont.)
??
n
1
??
??
15
??? ??
??
??
??
A B C . . . .
D1 D2 D3 D4 D5 D6 D7 D8 D9 . . .
R1 R2 R3 R4 R5 R6 R7 . . .
16
??? (cont.)
??
n
m
??
??
17
Todays Work
  • ???? ERD
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