We use Subversion and all we do is save the sql code in the directory for our subversion project and then commit the code to the repository when we are ready and update from the repository before we start working on something already in there.
The real trick is to convince developers to do that. Our dbas do that by deleting any stored proc (or other database object) that isn't in Subversion periodically. Lose stuff once and pretty much no one does it again.
