I've tended to do this in a new plan and then copy/paste the User View
query, then amend as needed, especially when it isn't working.
If you know your SQL works then you can paste in but may need to
change the syntax to match uPlan.
If it helps the User View is a temporary table that is assembled by
the SQL to match the main table at run time. This can be 1:1 or
1:many, and you can use UNION ALL to join queries together - there are
some docs on the support site that might help.
Phil, I tend to create multiple tables as needed in a fresh Access DB for each project (most of my work is assembling reports). Started using access as fairly easy and has fixed data typing. If you set the relationships correctly in access, the uPlan new plan wizard will create user views and adors for you, then easy to paste over and compare syntax.
I think Tim said at some point that one of the nice things about XMPie is the flexibility to easily add a flat file datasource late in the process with minimal effort.