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Chapter 29. Programming Combo and List B... > Constraining Query Choices with Comb...

Constraining Query Choices with Combo Boxes

Users of decision-support applications, especially managers, aren’t likely to be able to or want to use Access’s graphical Query Design window. Instead, most users prefer to pick criteria (SELECT query WHERE clause elements) from one or more lists of available options. One primary advantage of offering users a set of choices to construct a query is the ability to prevent execution of ad hoc queries that return an excessive number of rows. Accidentally returning thousands of rows or—even worse—a Cartesian product of a million rows or more can bring a multiuser application or the entire network to its knees. Network and database administrators call such events “queries from hell.”

Tip

Combo boxes are the better choice for generating WHERE clause criteria because they occupy less room on forms than list boxes. Also, you can navigate quickly to a combo box item by typing the first few characters of the item in the combo box’s text box element.



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