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Seminar: Introduction to relational databases

Seminar: Introduction to relational databases. Development process: Analyse the problem domain and build a conceptual model (ER model) Table design Domains Primary key, foreign keys, constraints Quality checking design (normalisation) Create tables Run queries.

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Seminar: Introduction to relational databases

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  1. Seminar:Introduction to relational databases Development process: Analyse the problem domain and build a conceptual model (ER model) Table design Domains Primary key, foreign keys, constraints Quality checking design (normalisation) Create tables Run queries Introduction to the database field: The development process FEN 2012-09-03

  2. Development Process Analyse the problem domain: Identify: • entities • relations FEN 2012-09-03

  3. Development Process Build the conceptual model: • Attributes • Primary keys • Cardinality • Participation FEN 2012-09-03

  4. Development Process Transform the ER model into relational schemas (tables): • 7 steps algorithm: • Entity -> Table(composite, and multi value attributes) • Weak entity -> Table(composite key, include owners key) • 1-1 and 1-n relations(include primary key from one side as foreign key on the other side) • n-m relations(new table with the primary keys from both sides as foreign keys, composite primary key) • Multi value attributes - > new table(include the owners primary key as foreign key) • Relations with degree > 2 -> new table(include all participants primary keys as foreign keys, composite primary key) FEN 2012-09-03

  5. Development Process Result: FEN 2012-09-03

  6. Development Process • Table Semantics • Avoid Redundant Information • Minimise NULL-values • Disallowing the generation of spurious tuples when joining tables. Informal Design Guidelines: Normalisation: • 1NF • 2NF • 3NF • BCNF • Look for functional dependencies / determinants that are not keys Not in 2NF! Not in 3NF! FEN 2012-09-03

  7. Development Process Guideline for Normalisation All attributes are to depend on the key, the whole key, and nothing but the key. So help me Codd. And remember: • FDs are business rules • Normalisation fights redundancy and other maladies in table design FEN 2012-09-03

  8. Development Process Table definitions: • Data types (domains) • NULLsallowed? • Primary key (ids?) • Referential constraints (FK-PK references) Constraint FEN 2012-09-03

  9. Development Process Execute queries: • SELECT, INSERT, UPDATE, DELETE • SELECT: • Rows and columns • Joins • Set operations FEN 2012-09-03

  10. The End! Thank you very much – hope you liked it. (fen@ucn.dk, http://public.ucn.dk/fen/Angers) FEN 2012-09-03

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