datediff是SQLSERVER中的用法，ORACLE没有1.功能：返回两个日期之间的时间间隔2.语法：datediff(datepart,startdate,enddate)是日期减去日期previousdateDate(enddate-startdate)1.datepart指定日期的哪一部分计算差值日期缩写yy/yyyyquarterqq/qMonthmm/mdaydd/dHourhh/hminutemi,nsecondss,s3.测试SQLSERVER不使用Writeselect...fromdual和ORACLE一样，只写select...。1.如果参数是yyyy，统计年份的差异，截取前4位进行统计selectdatediff(yyyy"20210928","20200121")test--selectdatediff(year,"20210928","20200121")test--selectdatediff(yy,"20210928","20200121")test
