upgrade to 1.7 st

i currently have 1.7 rc5 and want to upgrade to 1.7 final. will this override my existing database?

Your question is not very clear. You should always back up your database before performing an upgrade.

If you do the upgrade process your current database will be changed to include any database formatting changes between the two versions.

If you do the install process your current database will be wipe clean and re-setup empty.

Perhaps you would find this article beneficial:

http://www.tmib.net/how-upgrade-osticket-17rc6-17st(http://www.tmib.net/how-upgrade-osticket-17rc6-17st)