I am trying to load two xls files with the same structure/column names. I want to load them separately to different tables. If I use statement below, the results are messed up.
Plus my second question is, how I f.e. create a graph and use only data from Data table? Because I'm gettin' (You have attempted to apply a numerical expression, which is not uniquely defined for the specified variable. In order to use this variable in expressiona relying on number of occurrences, please read it a second time under a new name from its primary table) statement.
Usually there are quite rarely any benefits to load identically data-structures into different tables. Therefore I suggest to load them into a single table and if it's needed to differ between the tables you could add this as an additionally information, for example with: filebasename() as Source.