Union two objects in IDT

Hi,

Is there a way to Union two objects in Universe. I have an object called List number and this has NULL and Non-Null values. Customer wants both NULL and NON-NULL values to be displayed in the LOV of Webi query. I think this is not possible in Webi query, so wondering if i create an object with select null from dual and join with the Non-Null value object will yield the desired result.

Any suggestions?

Thanks,
Arun