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Normalization
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  • 1. CIS282
  • 2. Normalizing a database  Process of organizing data in database  Avoid duplicate values  Inconsistent dependencies  Each table describes one entity  Goal is Typically 3rd Normal Form  Each Form represents a different level  Each subsequent form requires that previous forms already in place  To be in Third Normal Form, must already be in First and Second Normal Form
  • 3. First Normal Form Each row/column combination has only one value Eliminate repeating groups  Instead of using a single field for all items purchased, set up item and quantity fields 1st Normal Form Not Normalized OrderID OrderID CustomerID CustomerID OrderDate OrderDate ItemID Items Purchased Quantity ItemName
  • 4. Second Normal Form Remove fields that are not fully dependent on the key, and place in separate table(s) ItemID is not dependent on the CustomerID and OrderID; it is dependent on OrderID. 1st Normal Form 2nd Normal Form OrderID CustomerID OrderID OrderID OrderDate CustomerID ItemID ItemID OrderDate Quantity Quantity ItemName ItemName
  • 5. Third Normal Form All non-key columns are mutually independent  ItemName depends on ItemID 3rd Normal Form 2nd Normal Form OrderID OrderIDOrderID OrderID CustomerID ItemIDCustomerID ItemID OrderDate QuantityOrderDate Quantity ItemName ItemID ItemName
  • 6. Normalization Summary A change in one field should not require change in another field in the table  No calculations All fields help describe the key  Each record is unique  Each table stores information about one “thing”