I had just used AF Table Lookup (2.5, of course) SUM feature. It works wonderful, when table contain some data relevant to query. But if table doesn't contain data, SUM result is NULL (not 0, as I've expected). But when I tried COUNT, COUNT gave me 0 as a result (what's appropriate because no data is zero data). I wonder if NULL is designed value for SUM with no data (or maybe 0 is more applicatible for this case).