In the table above, the order number serves as the primary key.  Notice that  the customer and total amount are dependent upon the order number -- this data is specific to each order.  However, the contact person is dependent upon the customer.  An alternative way to accomplish this would be to create two tables:

The creation of two separate tables eliminates the dependency problem experienced in the previous case.  In the first table, contact person is dependent upon the primary key -- customer name.  The second table only includes the information unique to each order.  Someone interested in the contact person for each order could obtain this information by performing a JOIN operation.

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Database Design
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