Let's say I have a script running and I want to find the last updated isbn number of the book during the run time with rails console.

Book.where(updated_at:Book.maximum('updated_at')).first.isbn

Then I can find how many books are updated during the runtime with this enhanced query

Book.pluck('isbn').uniq.find_index(Book.where(updated_at:Book.maximum('updated_at')).first.isbn)+1

Neat! Isn't it ?