Query of queries baby!
This works only in CF 5.0 but it works! The first two queries are from two different databases. The third queries the results of the two and joins on the origin.
Query of queries type functionality can be accomplished using SQL server or other DBMS, but CF will let you combine ANY type of query including LDAP queries (CFLDAP), email queries (CFPOP), or even Verity collections using CFSEARCH.
This is just an example.
<!--- access --->
<CFQUERY name="getApples" datasource="ds1">
select color,weight,origin from table_apples
</CFQUERY>
<!--- oracle --->
<CFQUERY name="getOranges" datasource="ds2">
select circumference,weight,origin from table_oranges
</CFQUERY>
<!--- get a combined record set filtered from the two previous record sets --->
<CFQUERY name="combined" datasource="query">
select
a.weight
, a.origin
, o.weight
, o.origin
from getApples a, getOranges o
where a.origin = o.origin
</CFQUERY>