select * from SiteMailManager smm where TIMESTAMPDIFF(second,'2012-07-03',smm.sendTimestamp)>0
sendTimestamp是当天的记录,即sendTimestamp减before argument大于0
update ManagerMail set sendSms=case when sendSms=1 then 0 else 1
方法二
UNIX_TIMESTAMP(NOW())-UNIX_TIMESTAMP(e.endTimestamp) >= 0