Are there any limitations joining between data sources?

There are two places where you can perform joins: (1) In a SQL statement on a single source, (2) Joining two sources together on the Source Description tab.

In the first case, you can make joins in the sql if the sources are compatible. For example, you can do a join between two pages in a spreadsheet or two separate text delimited files in the same folder. You could also do a join in the sql between two different Sql Server tables or even two different databases on the same server.

You cannot, however, do a SQL join between a spreadsheet and sql server table or between two separate Excel spreadsheet files.

PIESCentral will allow joins of unions. But if you need to create a join and then a union, it needs to be done in the sql and may not be possible.