Data duplication in databases

Hi, Don't know if this is the best place to ask, but I thought I would give it a try. I was just wondering if anyone knows of any databases which deal with data duplication (at a low level). Say I have two (or ten) identical records, does anyone know of any databases which would only keep one copy of the data and use references for the other records? Does this work if 7 out of the 8 columns (for instance) are identical (ie the primary key is different but everything else is identical). Do such db's exist? Or do they all do this? Or am I just dreaming? J -- Julian Wood Programmer/Analyst University of Calgary