datetime diff in mysql code example

Example 1: mysql time ago difference

#Need item created 12 hours ago or newer. Discards older than 12 hours
	 created_at >= (NOW() - INTERVAL 12 HOUR)

Example 2: mysql timediff

SET @date1 = '2010-10-11 00:00:00', @date2 = '2010-10-10 00:00:00';
SELECT 
  TIMEDIFF(@date1, @date2) AS 'TIMEDIFF',
  TIMESTAMPDIFF(hour, @date1, @date2) AS 'TIMESTAMPDIFF';