Select using DBnull

How can i select data in my report based on DBnull values.

I want to select the data from table 'A' whose corresponding certain field value in table 'B' is DBnull, using Select Expert. How can i do this ? The corresponding field in Table 'B' is String or Date.

Assuming you are using Crystal reports you would need to base the criteria on a Formula. The Formula code would be

IsNull({Name of Field})

Crystal will then add the above to the SQL statement it generates ie

Where [Name of Field] Is Null