Parameter value “Set to Null” is sometimes activated, but sometimes not

Parameter value “Set to Null” is sometimes activated, but sometimes not

Dear all,

I am using Crystal reports 2008 SP6. I have created a report based on a BW query. The parameters were created automatically after I have embedded the query.

When I execute the report, some variables have the flag “Set to Null” already activated, some others not. See also this screenshot.

Where can I define the default value for having the option “Set to Null” activated? I was not able to find anything in the parameter properties. If this cannot be defined in the report designer somewhere, how I can influence whether a variable has this option already activated by default?

Any idea would be great. Best regards,

Stefanos from Munich/Germany