Well, I made a backup of my forum a day before the hosting site went under maintenance and my files were unavailable for 3 days. I moved the backup to another host and unzipped, but about 20 posts and 1 user were lost because the backup did not cover them. Now, users have joined the new host and posted, and the now old one is back up. How can I merge the two databases without causing conflicts?
If it's really only 20 posts, that's little enough to do it manually or even not do it at all but ask the users to copy their posts over if they even want to keep em.
If it was a larger number you could script something for it. The problem is that your restored forum will have posts with the same post ids as the missing posts from your old forum. So you can't just insert the missing ones into your new board, not with the same post ID anyway.