I have a list of customers for the year 2013, 2014, 2015. I want to exactly identify records of those customers whom we have lost i.e. customer records that are not appearing in the year 2015 - with a remark on each record which year we lost. Job requires triangulation of various unique fields, e.g. engine #, vehicle registration number, car make, customer name, Mobile Number etc. to pin point lost customers.