I have a query
base query | stats count by ABC | fillnull
but i am getting "no result"
instead of this, i want to display ABC count as "zero"
I don't entirely follow what you're trying to achieve, but the purpose of fillnull is to populate empty fields with a null value, not to generate results when there are none. When the stats command returns 0 results, there is nothing to apply "fillnull" on.
If you can elaborate a bit more what you want to achieve (and if possible show some sample data and expected outcomes) we can try and help you find a solution that does work.
base query | stats count by ABC | appendpipe [ stats count | eval "NoResults"="0" | where count=0 |table "NoResults"]