CHAPTER 6 BUILDING REPORTS
Figure 6-26. Report Properties dialog box, showing the Allow Null Value fieldDefault parameter values will also need to be manually configured. If no default parameter value is
assigned to an available parameter, the report, when rendered or previewed, will not process the
incoming data until a user supplies a value. Previewing the report without modifying the parameter
selection reveals that the user would need to enter a value for each parameter that has no default value
assigned. The user would not be able to choose from a list of values, but would have to enter them
manually. This is often unacceptable because the user may not always know the correct values to enter;
good examples of this are the EmployeeTblID field that is used to select a specific employee and the
BranchID field used to retrieve the branch name.
The first step is to provide valid query-assigned values for the parameter drop-down lists. It would
be beneficial to provide a view of the report in preview mode prior to adding descriptive parameter
values from a new dataset (see Figure 6-27). Notice that there is a NULL checkbox selected next to the
parameter selections. The NULL checkboxes appear when the parameter allows NULL values, as you set
earlier, and there are no other available values.