VC query filter for empty value

Hi community,

i'm using BPM_MY_PROCESSES_DS as datasource and i want to set filter for empty field values. For example, give me all records where PARENTID is empty / initial / null. I tryed it with:

=null --> no success (returns all values as if i would pass nothing to the filter)

="" --> same result as =null

="#" --> gives me error that '#' not allowed. But VC visualizes empty values in a result with this hashtag

So how can i achieve this. I do not want to load all records and set a filter later because then i would have to load about 8 times more data.

Any help appriciated.

Best regards,

Tobias