Entity relationship modeling
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Entity-Relationship Modeling. ER. Graphical modeling technique Informal, understandable for laymen Coarse technique to design tables Provides rules of thumb for mapping to table structures. Entities and attributes. Relations (associations). Recursive relations. With roles. Weak entities.

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Entity-Relationship Modeling

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Entity relationship modeling

Entity-RelationshipModeling


Entity relationship modeling

ER

  • Graphical modeling technique

  • Informal, understandable for laymen

  • Coarse technique to design tables

  • Provides rules of thumb for mapping to table structures


Entities and attributes

Entities and attributes


Relations associations

Relations (associations)


Recursive relations

Recursive relations

With roles


Weak entities

Weak entities


Isa hierarchy

ISA-hierarchy


Cardinality optionality

Cardinality & optionality

(0,n) (1,1)

optional mandatory


Erd relational schema

ERD -> relational schema


Erd relational schema1

ERD -> relational schema

Solution 1

E1 (K1, A1, …, Am, K2)

E2 (K2, B1, …, Bn)

Solution 2

E1 (K1, A1, …, Am)

E2 (K2, B1, …, Bn, K1)


Erd relational schema2

ERD -> relational schema

Solution 3

E1 (K1, A1, …, Am, K2)

E2 (K2, B1, …, Bn, K1)


Erd relational schema3

ERD -> relational schema

Solution 4

E1 (K1, A1, …, Am)

E2 (K2, B1, …, Bn)

R (K1, K2)


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