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Progettazione Logica

Progettazione Logica. Giorgio Ghelli. The relational data model. All data in flat tables of rows with a primary key (access operators: later) Associations as foreign keys. The relational data model: graphic notation. Employees. Departments. . 1. Employees. Departments.

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Progettazione Logica

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  1. Progettazione Logica Giorgio Ghelli

  2. The relational data model • All data in flat tables of rows with aprimary key(access operators: later) • Associations as foreign keys

  3. The relational data model: graphic notation Employees Departments  1 Employees Departments

  4. Phases of database design • Conceptual design • Logical design • Physical design

  5. Translating a conceptual plan to the relational model • Add an artificial primary key to any collection which needs one • Translate associations and inclusions into foreign keys • Flatten complex attributes • Translate multivalued attributes into tables

  6. Translating a conceptual plan • 1-N associations become foreign keys departments departments employees employees

  7. M-N associations • Encoded as a table with two foreign keys

  8. M-N associations • M-N associations become tables • They get association attributes projects projects ProEmp Percentage Percentage employees employees

  9. Subcollections • Conceptual: • Persons(PId, Name) • Employees ext Persons(Dept, Salary) • Consultants ext Persons(Project, Fee) • Logical: ?

  10. Subcollections • Conceptual: • Persons(PId, Name) • Employees ext Persons(Dept, Salary) • Consultants ext Persons(Project, Fee) • Logical: • Persons(PId, Name) • Employees(Dept, Salary, PId*) • Consultants(Project, Fee, PId*) • Persons(PId, Name, Kind, Dept, Salary, Project, Fee)

  11. Subcollections pId persons name code pId persons dept employees name salary dept employees salary code persons name kind dept salary

  12. All together, now father-of persons families inhabits tax-payers flats percentage

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