Briefly looking at the data, however,I'd hazard a guess that the form links to the attachment by AttachmentUID, as both fields appear in both tables.

As said above, it's apparent that whoever was doingthis didn't really know what they were doing (they probably had some impression that 1 database = 1 table).

You could probably run something like this to get some information:

SELECT *

FROM application.dbo.FormAttachment FA

JOIN evaluationAttachment.dbo.Attachment A ON FA.AttachmentUID = A.AttachmentUID

I'd try testing that with a few knowns in your where clause first, as that could be a very big data set, depending on your database.