I tried union, i think union is possible only on the tables coming from the same database. But in my report tables are coming from different databases. So i am not able to perform union.
Bring both datasources into your workbook and then join them by a common field using the Relationship Editor under the Data menu.
Hi Rohit - yeah you're right. The 'out of the box' union function requires the same connection so in your case the same Access database. I've done a bit more searching and found this post by zen master Jonathan Drummey that may have the solution you're looking for Cross Data Source Joins + Join on Calcs = UNION Almost Anything in Tableau v10.2 | Drawing with Numbers . It'll take a bit of reading and time to understand but hopefully it'll get you what you need. I haven't tried it myself though.