select to_char(createtime,'yyyyMMddHHmiss') createdate,limitnum,(length(replace(rpad(substr('0111110',to_char(createtime,'D')),sysdate-createtime+1,'0111110'),'0','')))-(limitnum/(24*3600000)) overtimedate from WFWORKITEM where workitemid='10403'我overtime计算的是从sysdate到createtime之间有多少工作日(排除limitnum的时间),我如何把overtime改成两者之间相差有多少个工作小时呢?