A computer system compares databases, where each data record includes values for a plurality of fields, by applying database operations on database tables of the data records to reduce computations being performed. For each data record in a reference set, candidate matches are identified from among the data records in a target set by performing a join operation on the sets on one or more selected, normalized fields from the sets. This significantly reduced set of candidate matches can be further analyzed to determine how similar they are to the data record from the reference set.