1.计算时间差(相隔星期,天数,小时,分钟,秒) SELECT TO_CHAR(date1,'MMDDYYYY:HH24:MI:SS') date1, TO_CHAR(date2,'MMDDYYYY:HH24:MI:SS') date2, trunc(86400*(date2-date1))- 60*(trunc((86400*(date2-date1))/60)) seconds, trunc((86400*(date2-date1))/60)-60*(trunc(((86400*(date2