I have a query made up of two subqueries. The subqueries run fine. In the master query I join the subqueries by ID and add an ORDER BY clause. But when I try to run it, I get the "too complex" error.

Here's the master query:

SELECT qryBusByCntrySTISub.Country AS CountrySTI, qryBusByCntrySTISub.STIEligible, qryBusByCntrySTISub.STIPool, qryBusByCntrySTISub.STISpend, qryBusByCntrySTISub.AverageSTI, qryBusByCntrySTISub.PofBaseSalary, qryBusByCntrySTISub.DNA, qryBusByCntrySTISub.PA, qryBusByCntrySTISub.SA, qryBusByCntrySTISub.E, qryBusByCntrySTISub.SE, qryBusByCntryBSRSub.Country AS CountryBSR, qryBusByCntryBSRSub.BSREligible, qryBusByCntryBSRSub.DiscretionaryBudget, qryBusByCntryBSRSub.DiscretionaryIncrease, qryBusByCntryBSRSub.AverageIncrease, qryBusByCntryBSRSub.YoYIncrease, qryBusByCntryBSRSub.YoYG10, qryBusByCntryBSRSub.Promotions,
(qryBusByCntrySTISub.Country + qryBusByCntryBSRSub.Country) AS Sorter
FROM qryBusByCntryBSRSub LEFT JOIN qryBusByCntrySTISub ON qryBusByCntryBSRSub.Country = qryBusByCntrySTISub.Country
UNION SELECT qryBusByCntrySTISub.Country AS CountrySTI, qryBusByCntrySTISub.STIEligible, qryBusByCntrySTISub.STIPool, qryBusByCntrySTISub.STISpend, qryBusByCntrySTISub.AverageSTI, qryBusByCntrySTISub.PofBaseSalary, qryBusByCntrySTISub.DNA, qryBusByCntrySTISub.PA, qryBusByCntrySTISub.SA, qryBusByCntrySTISub.E, qryBusByCntrySTISub.SE, qryBusByCntryBSRSub.Country AS CountryBSR, qryBusByCntryBSRSub.BSREligible, qryBusByCntryBSRSub.DiscretionaryBudget, qryBusByCntryBSRSub.DiscretionaryIncrease, qryBusByCntryBSRSub.AverageIncrease, qryBusByCntryBSRSub.YoYIncrease, qryBusByCntryBSRSub.YoYG10, qryBusByCntryBSRSub.Promotions,
(qryBusByCntrySTISub.Country + qryBusByCntryBSRSub.Country) AS Sorter
FROM qryBusByCntryBSRSub RIGHT JOIN qryBusByCntrySTISub ON qryBusByCntryBSRSub.Country = qryBusByCntrySTISub.Country
ORDER BY Sorter;

If I eliminate the full outer join the error goes away. But I need it.

I fixed it. I don't know why it worked though. It was due to some null values in the DB. Still don't understand why those null values are fine on an inner join or left join or right join, just not in a full outer join.