Here's the Quickstart on Cross Data Base joins from the Tableau Help:
It advises a few solutions for fixing broken joins. Did you try "Use calculations to resolve mismatches between fields in a join" in this topic:
Hope this helps!
Please do explicit data type casting in custom SQL queries for each of the sources and it should work.
Did you ever figure out the solution Keerthana? I'm experiencing a similar issue trying to connect a CSV and an SPSS SAV file. I've manually changed the data types to match, but keep getting the error message that the types are mismatched. I'm using 10.4.
Can you share your packaged workbook saved as a 10.2 format?
Unfortunately, no due to the sensitive nature of the data.