The logic is not correct. What if price is 2 from trans1 table, and price is 3 from trans2 table? Then the UNION will get both records.
I think you need something like thisselect Region_ID,
[Agency ID],
Customer_Number,
Document_Number,
document_Date,
min(Price)
From (
select Region_ID,
[Agency ID],
Customer_Number,
Document_Number,
document_Date,
Price
from trans1
union all
select Region_ID,
[Agency ID],
Customer_Number,
Document_Number,
document_Date,
Price
from trans2
) as d
Group by Region_ID,
[Agency ID],
Customer_Number,
Document_Number,
document_Date
Peter Larsson
Helsingborg, Sweden