What is the difference between using .exists?, and .present? in Ruby?

Question

I want to make sure I\'m using them for the correct occasion and want to know of any subtleties. They seem to function the same way, which is to check to see if a object fi

Answer 1

SELECT COUNT(*) would scan the records to get a count.

SELECT 1 would stop after the first match, so their exec time would be very different.