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Entity-Relationship Modeling

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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  1. Entity-RelationshipModeling

  2. ER • Graphical modeling technique • Informal, understandable for laymen • Coarse technique to design tables • Provides rules of thumb for mapping to table structures

  3. Entities and attributes

  4. Relations (associations)

  5. Recursive relations With roles

  6. Weak entities

  7. ISA-hierarchy

  8. Cardinality & optionality (0,n) (1,1) optional mandatory

  9. ERD -> relational schema

  10. 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)

  11. ERD -> relational schema Solution 3 E1 (K1, A1, …, Am, K2) E2 (K2, B1, …, Bn, K1)

  12. ERD -> relational schema Solution 4 E1 (K1, A1, …, Am) E2 (K2, B1, …, Bn) R (K1, K2)

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