Wanted to get an idea on how to side by side comparison of product features (in this case they are actually laboratory characteristics). The data will be stored in a table with 3 fields (sample_id, characteristic, result) and users will be able to check up to 5 different samples and after clicking compare button should be directed to a page with up to 6 columns listing each characteristic in first and then up to 5 samples. If all samples have the same characteristic, this is easy. However, they all can have up to 300 diff characteristics, some having 40, some 60, some 20, etc. I only want to show the interlapping characteristics. So...can anyone give me some pseudo code on how this can be done? Or if you have an example? Any help would be greatly appreciated.