Part of my job involves going in and hand-altering our production databases on a regular basis, and occasionally repairing production servers. Don't ask... just take it as a given. The other half of my group is a guy who is wicked fucking smart, but was very junior when he started. He can pretty much always figure out how to do what needs to be done, but I've been teaching him good habits-- things like always make a backup before you fuck with something, have a second person watch over your shoulder for big changes, and for databases always use transactions and doublecheck your changes before you commit them.
Apparently while I was in Vegas he screwed up a change and typed:
update table set foo=x, bar=y
update table set foo=x where bar=y
and because I'd taught him good habits he was able to recover and undo the change with one rollback rather than a full database restore.
It's a rite of passage for any tech person to make a big mistake and fuck up a system. The lucky ones learn why they should be thankful for having been taught good data-handling practices. The unlucky ones learn how to mop up after a big mess.
My coworker and I have independently concluded that MySQL should alias the word "fuck" to "rollback".