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
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
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
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
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”
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