[ndriscoll]

If you're going to run commands that modify data directly on the cli, do it in a transaction so you can roll back. Also, start with `--` to make it a comment. Once you have the correct query and someone's checked your work, go back to the beginning of the line and remove the `--` so you can run it. It's also a good idea to write a select * or count first to check that things make sense, and then start your transaction, go up and modify your select into a delete/update, check affected rows looks good again, maybe do another select or two to check that data looks like you expect, commit.

[Izkata]

Fun fact: if you still have a MySQL (MyISAM) database, the transaction commands return success but don't actually function, so you can't roll back.