I'm a rookie using Tableau so this might be an easy one to answer... I've one Orders header table (2017 to Date) and a Orders detail table (2017 to date), which I'm left joining in Tableau by the Order ID, everything works perfectly, but the issue is that I have a third table that contains Orders History (Prior 2017) and is already merged into a single table (Header and Detail). This History table contains all of the fields that the details and the header table have, which is the best way to approach this, I've tried UNION the History to both Header or Detail but I don't feel is correct as History table has all of the fields I get duplicated fields either ways.
I almost filed that I should consolidate header and detail tables outside of Tableau and then just UNION this resultant table with the history in tableau (?)
Maybe I'm over complexing this. Any kind of help will be sincerely appreciated.
Unless I am misunderstanding I believe you could append the files together using the "Append Data from File" in Tableau Desktop.
More information can be found above.
Hope this helps!