There are various ways to integrate different datasets. You may extract and generate common feature from the dataset and integrate the datasets in similar fashion as people do in relational or object oriented databases. There is need to be specific over dataset.
the best way is to have a common data in both files and therefore concatenate all files while keeping individual file information. it's easy in xls, you just need to keep the same structure (column informations) for both files in the new file.
The integration of various dataset depends on the format, volume and type of data. A framework for integrating big medical data was proposed in this article:
Article In Search of Big Medical Data Integration Solutions -A Compr...