You can provide users who are database-savvy with the option of selecting rows when a field has a null value. Databases use a null value to indicate that there is no data in that field. A user might find it useful, for example, to view customer data where a customer’s credit-limit field is null, because null in this field means that the customer account is new, and a credit limit has not been set. For string data, a null value is not the same as a blank value or an empty string (" "), which is an actual value. Blank values apply to string fields only. Null values apply to all data types.

You can create a report parameter that provides users the option to match null and blank values. Figure 13‑26 shows Enter Parameters displaying two parameters that provide the null and blank value options. The Threshold Quantity parameter uses a text box, and the Product Vendor parameter uses a list box. To specify a null value for the first parameter, the user selects Null Value. To specify a blank value for the second parameter, the user selects the empty item at the top of the list.

This procedure assumes that you already created a report parameter.