If you want to store data in a compressed format, whatever you retrieve will also be in compressed format, so you'll need to do the compressing/uncompressing yourself. The datatype to use would probably be a BLOB, which requires a JDBC 3.x driver. If I remember correctly, the Sun JDOC/ODBC bridge only supports a subset of JDBC 3, so you may need to find a better driver. (And I have no idea if Access even supports BLOBs).
On an unrelated note, next time you should ask a question like this in the JDBC forum, as it has nothing to do with servlets (and I won't even go into how servlets provide a multi-threaded environment in which Access and the JDBC/ODBC bridge can cause all kinds of problems). [ September 06, 2005: Message edited by: Ulf Dittmer ]