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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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Presentation on theme: "Complex entities and relationships Case examples are from the book: Lars Fank Databaser Teori og Praksis ISBN 87-571-2397-7."— Presentation transcript:

1 Complex entities and relationships Case examples are from the book: Lars Fank Databaser Teori og Praksis ISBN

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

3 Repetition: One-to-many relationships

4 Repetition: Many-to-many relations.

5 Different illustrations of tree structure relationships:

6 Different illustrations of network structure relationships:

7 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

8 Different illustrations of simple relationships of order 3.

9 Different illustrations of simple relationships of degree 3.

10 ER and Bachman illustrations of the relationship of order three.

11 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?

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

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

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

15 End of session Thank you !!!


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