I haven't explored the TabCMD option of doing this yet because I want this to happen automatically as part of a Tableau Job Schedule and I don't believe you can use TabCMD in a schedule. The problem I'm facing is that when the workbook is refreshed each of the 3 data sources is refreshed BUT they are never appended together on the server. ie; the VIz shows only data from 1 source!!.
In Tableau 10 (desktop) this is done manually by right clicking on the data source then "Extract--> Append Data From Data Source". But Server fails to do this when it refreshes.
All I am trying to do is UNION 3 separate data sources together (3 different SQL databases) and have them auto refreshed weekly. Same data structure/ data types. This only seems possible in Excel using UNION as part of the SQL where you combine data from multiple sheets. But I need this to happen across Databases. I tried to Full Outer Join the databases but the desktop product does not seem to allow Full Joins. So it seems to me that there is big Hole in Tableau.
If anyone has any pointers (must be automated) then I'm all ears.