1 entity-relationship modeling. 2 er graphical modeling technique informal, understandable for...
TRANSCRIPT
![Page 1: 1 Entity-Relationship Modeling. 2 ER Graphical modeling technique Informal, understandable for laymen Coarse technique to design tables Provides rules](https://reader036.vdocuments.site/reader036/viewer/2022062511/551b516c550346ae7a8b52d9/html5/thumbnails/1.jpg)
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Entity-RelationshipModeling
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2
ER
• Graphical modeling technique
• Informal, understandable for laymen
• Coarse technique to design tables
• Provides rules of thumb for mapping to
table structures
![Page 3: 1 Entity-Relationship Modeling. 2 ER Graphical modeling technique Informal, understandable for laymen Coarse technique to design tables Provides rules](https://reader036.vdocuments.site/reader036/viewer/2022062511/551b516c550346ae7a8b52d9/html5/thumbnails/3.jpg)
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Entities and attributes
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Relations (associations)
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Recursive relations
With roles
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Weak entities
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ISA-hierarchy
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Cardinality & optionality
(0,n) (1,1)
optional mandatory
![Page 9: 1 Entity-Relationship Modeling. 2 ER Graphical modeling technique Informal, understandable for laymen Coarse technique to design tables Provides rules](https://reader036.vdocuments.site/reader036/viewer/2022062511/551b516c550346ae7a8b52d9/html5/thumbnails/9.jpg)
ERD -> relational schema
![Page 10: 1 Entity-Relationship Modeling. 2 ER Graphical modeling technique Informal, understandable for laymen Coarse technique to design tables Provides rules](https://reader036.vdocuments.site/reader036/viewer/2022062511/551b516c550346ae7a8b52d9/html5/thumbnails/10.jpg)
ERD -> relational schema
Solution 1E1 (K1, A1, …, Am, K2)E2 (K2, B1, …, Bn)
Solution 2E1 (K1, A1, …, Am)E2 (K2, B1, …, Bn, K1)
![Page 11: 1 Entity-Relationship Modeling. 2 ER Graphical modeling technique Informal, understandable for laymen Coarse technique to design tables Provides rules](https://reader036.vdocuments.site/reader036/viewer/2022062511/551b516c550346ae7a8b52d9/html5/thumbnails/11.jpg)
ERD -> relational schema
Solution 3E1 (K1, A1, …, Am, K2)E2 (K2, B1, …, Bn, K1)
![Page 12: 1 Entity-Relationship Modeling. 2 ER Graphical modeling technique Informal, understandable for laymen Coarse technique to design tables Provides rules](https://reader036.vdocuments.site/reader036/viewer/2022062511/551b516c550346ae7a8b52d9/html5/thumbnails/12.jpg)
ERD -> relational schema
Solution 4E1 (K1, A1, …, Am)E2 (K2, B1, …, Bn)R (K1, K2)