how bout this
Code:
SELECT aa.aa AS [name], AVG(aa.Value) AS [Value],cd_clients.cy, cd_clients.tax, cd_clients.fee, cd_clients.retro FROM aa INNER JOIN cd_clients ON aa.aa = cd_clients.aa WHERE aa.Date BETWEEN #01/01/2006# AND #03/31/2006#
The inner join will only work if there are always values in both tables, otherwise you would want to use an outer join