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Published byMariano Brewton Modified over 2 years ago

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Complex entities and relationships Case examples are from the book: Lars Fank Databaser Teori og Praksis ISBN 87-571-2397-7

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Short repetition: Many-to-many, One-to-many, trees, and network relationships:

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Repetition: One-to-many relationships

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Repetition: Many-to-many relations.

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Different illustrations of tree structure relationships:

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Different illustrations of network structure relationships:

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Relationship degree Type of relationshipRelationship degree One-to-many relationshipBinary Many-to-many relationshipBinary One-to-one relationshipBinary Tree structure relationshipUnary Network relationshipUnary Order relationshipUnary Relationship of degree NN-ary

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Different illustrations of simple relationships of order 3.

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Different illustrations of simple relationships of degree 3.

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ER and Bachman illustrations of the relationship of order three.

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An ER relationship need not be implemented as a table or a forign key How would you convert the Bachman diagram to an ER-diagram with normalized tables?

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Entities and relationships must not be connected directly in ER-diagrams. Therefore, ER-diagrams need a pseudoentity if two relationships need to be connected

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ER relationships may be viewed as Bachman entities depending on the application area.

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ER versus Bachman diagrams: In this course you should not use ER-diagrans because they are ambiguous

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End of session Thank you !!!

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