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Keys

Each table in your database represents one subject only. But as you've seen, to accomplish your mission objectives, you need data from two, three, or even more of these tables. For example, the invoice you looked at earlier requires values from the Customers, Orders, and Order Details tables, and perhaps other tables as well. Having segregated your data by subject, how do you now tie together these tables so you can combine their values and accomplish your mission objectives?

Keys are a vital part of the answer. Keys are essential for ensuring that each record in a table is uniquely identified. You'll soon see that achieving that objective is crucial if you hope to bring together data from several tables while maintaining data integrity.


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