Thanks for your reply. There is no relation between the tables as they are metrics of different processes. All of them transaction tables with few (2 or 3)common dimensions across them. So i can't use joins or Mappings.
If the transaction tables are nothing alike, but you want to create a couple of dashboards, you'll have to build a sort of datamodel so that all of the data gets displayed correctly. (Otherwise, you're building 40 different versions of the same dashboard most likely)
Things to consider would be:
Do you need all the fields (columns)
Which fields have the same type of value, but have different names
Things like this will help you solve the issue at hand and consolidate the 40 different data sources into a workable datamodel.