I do mysql-mon, mysql-tues, ..., mysql-sun, and leave timestamping for uniqueness to the backup. That way, I don't have to go and find my old dumps to delete them; they just get overwritten weekly.
Why not have your database program dump to a backup directory before amanda comes in? If you've got the disk space this makes the most sense.
One thing to do though: if you're going to keep history, don't name your backups dbdump.1, dbdump.2, dbdump.3, etc. When you rotate them out the timestamp on ALL of them change, so amanda has to tape all of them again. Using a slightly smarter system do produce dbdump.20040101, dbdump.20040102, dbdump.20040103, etc. makes things better.
$.02,
-Ken
