Nope. No standard "oops" methods to undo mistakes - that is what Transactions are there for.
The best solution is to reload from your last backup - you do backups, don't you? - and then re-enter any changes. If you don't have a backup, then it gets horribly complicated and will depend on the logging level your DB uses - and it'll probably cost you money:
Google[
^]
If this is your development database then it's not going to be a problem: just recreate it. If it's your production DB though, you need to talk to your boss quickly, because you may have a major problem and he will find out. It's better if you bring it to his attention ASAP so the actual damage can be minimised.