delete from table where (unix_timestamp(fielddatetime)+7200)<unix_timestamp()
delete from table where date_add( fielddatetime,INTERVAL 7200 second )<now()
delete from table where date_add( fielddatetime,INTERVAL 120 minute )<now()
delete from table where date_add( fielddatetime,INTERVAL 2 hour)<now()
delete from table where timediff(NOW(), fielddatetime)>'02:00:00'
ลำดับการเปรียบเทียบเร็วไปหาช้า
bit, byte, word, dword
interger, float, string