Chapter 8

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Chapter 8

  1. 1. David Morales<br />Chapter 8<br />
  2. 2. Normalization<br />The process of organizing data in tables in a form that is useable in a data base<br />Tasks involved in Normalization:<br />Removing repetitive information<br />Making sure each record occupies only one row<br />Determining a piece of data that will uniquely identify each row<br />Establish how each table’s data relates to other tables<br />
  3. 3. Entity-Relationship Diagram (ERD)<br />Model that shows logical relationships and interaction among system entities<br />The Transaction liking the entities, logs hours on, is a third entity with its own characteristics, this entity is called an associative entity<br />M and N denote the relationship as many to many<br />Many employees may logs hours on different projects<br />Logs hours on<br />Employee<br />Projects<br />M<br />N<br />Time Keeping<br />
  4. 4. ERD With Cardinality Notation<br />The marks by the entities represent their cardinality<br />Cardinality the numeric relationship and shows how instances of one entity relate to instances of another<br />In the example one employee, or many employees, or none, can log hours on one project, many projects or no projects<br />Logs hours on<br />Employee<br />Projects<br />Time Keeping<br />
  5. 5. Tables for Entities in 3NF<br />Employee<br />Projects<br />Associates records in time keeping <br />with records in Employee<br />Associates records in time keeping <br />with records in Projects<br />Sum total of all hours in records in Time Keeping with corresponding the project #<br />Time Keeping<br />
  6. 6. Tasks<br />Indentify all entities<br />Create an initial ERD<br />Assign all data elements to entities<br />Verify all data dictionary entities<br />Create tables in standard notation<br />
  7. 7. Tasks<br />Remove repeating groups (1NF)<br />Remove fields from a table if not dependant on Primary key (2NF)<br />Ensure every non-key field depend on the key, the whole key and nothing but the key<br />Identify Keys<br />Identify table relationships<br />
  8. 8. Concurrent Tasks<br />Identify all entities<br />Assign all data elements to entities<br />Verify all data dictionary entities<br />
  9. 9. Sequential Tasks<br />Create an initial ERD<br />Create tables<br />Identify keys<br />1NF<br />2NF<br />3NF<br />Identify table relationships<br />

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