A nice little piece of nothing this one.
I noticed on the forums, someone asking about these functions. So, I did some digging.
I built a first query that list stores :
The query became something like :
Then, I based a query on it:
the query became :
( Outlet_Lookup.Shop_id=Shop_facts.Shop_id )
AND ( Article_lookup.Article_id=Shop_facts.Article_id )
at the next iteration, it became:
and when I tried filtering for a number, it became:
This tells me, it’s not a user-function. It’s an internal function. The user is expected to use a subquery instead.
Or, as Andreas stated on the forums : query on query, which allows you to filter based on a different datasource.