Sams Teach Yourself SQL in 10 Minutes

Understanding Calculated Fields

Data stored within a databases tables is often not available in the exact format needed by your applications. Here are some examples:

• City, State, and Zip are stored in separate columns (as they should be), but your mailing label printing program needs them retrieved as one correctly formatted field.

• Column data is in mixed upper- and lowercase, and your report needs all data presented in uppercase.

• An Order Items table stores item price and quantity, but not the expanded price (price multiplied by quantity) of each item. To print invoices, you need that expanded price.

• You need total, averages, or other calculations based on table data.

In each of these examples, the data stored in the table is not exactly what ...