Upgrading (HSQLDB)

Hi The quickest way to upgrade a xwiki installation running on jetty+hsqldb would be to unzip and to overwrite all files under db/ with the "old ones". But does it work like that? For example, I have a 0.840 and a 0.1252. I want to move them to the latest svn. Do I lose something if I overwrite the files this way? Thank you. Marc