I always do destructive SQL commands in two steps: first run a select using the WHERE clause you intend to use and verify which records will be affected, then hit the up arrow and edit the beginning of the query leaving the WHERE intact.

I also like adding redundant conditions to the WHERE so a typo in any single one of them won't sink me.

A related Bash command: alt+# to prepend a hash symbol and submit the line, so you can return to it later (through Bash's history) to run it.

I use an alternate version on SQL: when running any modification on any kind of sensible database (which is a bad practice in itself, obviously, but sometimes you don't have a choice), always type in the WHERE clause before the table name (added bonus: do a SELECT first with that clause to see what you are modifying).

That way, if you accidentally send it, the command fails and nothing happens.

For SQL, always BEGIN first. If you’re unsure, run it as an EXPLAIN first. Then fire. Then commit it or roll back.

Especially useful if you're remoted in over a laggy connection.