I use crystal reports 2008 and wanted to know if parameters can be left blank? i did write a formula to do that but it didnt work. I did set the optional parameter ti true in the parameter edit box and wrote this formula in the record selection.
not HasValue ({?param1}) or
{table.field}={?param1}
Dont know if there is any other way this can work because there are several parameters and they want to leave some parameters it blank.