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Queries Ask Questions

You discovered in the last chapter that the table is the heart of the database. A good database plan can help you organize your table data. But organization is not the only function of a database. You might need to compare last year’s table with this year’s table. Or you might want to update one field’s data throughout the entire table. Or you might need to compute the sales tax on all the invoices in the table. And the list goes on. In other words, you need a vehicle that can manipulate and examine data in a variety of different ways.

What is a query? It is simply a program that asks a question pertaining to table data. You can consider a query a description of the records you want to retrieve from your table data. That description usually includes a criterion (plural, criteria), which is a condition or a test by which record selection is determined. This condition in the query takes the form of an expression, which was covered in Chapter 3. How many claims in the state of Missouri are more than $5,000 in the period between July 1, 1994, and June 30, 1995? This is a typical question that could easily be converted to a criterion for a query.


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