Are all of the data set formats the same? Do they need to be the same for your analysis? Do all fields contain the same labels? Does the data with similarly titled labels contain the same type of data? How are the files delimited? Are there any extra delimiters that may cause problems when importing? What strategies can you use to deal with any of these challenges? Is the data structured or unstructured? What transformation would be needed to any unstructured data to make it possible to analyze it? Is the data aggregated at the same level