You might not always know the parameters for the query output when you're designing a query—and your application's users also might not know the parameters. Parameter queries let you specify specific criteria at runtime so that you don't have to modify the query each time you want to change the criteria.
For example, imagine you have a query, like the one shown in Figure 15.7, for which you want users to specify the date range they want to view each time they run the query. You have entered the following clause as the criterion for the OrderDate field: