I have a portfolio of bank loans that are segmented into seven subgroups. Each subgroup has its own set of tables and queries. The queries for each subgroup work fine. I created a Union query to try to create a report that brings all the data together.
In all, there are probably at most 100,000 records of data across these tables. There are about 50 queries in total that are run (for example - the "commercial" portfolio queries total 10; the "credit card" portfolio queries total 3 - etc.
The ACCESS model was built by some outside consultants who are long gone. (I would not have built it the way they did -- they created a different query for each step in the logic rather than combine it all in one or two queries.)
ADDED -
If I create two union queries - one reporting on the 1st 4 subgroups and the second reporting on the last three subgroups - these work fine.