SQL Server DateDiff Example

Unit of time	Query	Result
NANOSECOND	SELECT DATEDIFF(NANOSECOND,'2011-09-23 17:15:22.5500000','2011-09-23 17:15:22.55432133')	4321300
MICROSECOND	SELECT DATEDIFF(MICROSECOND,'2011-09-23 17:15:22.5500000','2011-09-23 17:15:22.55432133')	4321
MILLISECOND	SELECT DATEDIFF(MILLISECOND,'2011-09-23 17:15:22.004','2011-09-23 17:15:22.548')	544
SECOND	SELECT DATEDIFF(SECOND,'2011-09-23 17:15:30','2011-09-23 17:16:23')	53
MINUTE	SELECT DATEDIFF(MINUTE,'2011-09-23 18:03:23','2011-09-23 17:15:30')	-48
HOUR	SELECT DATEDIFF(HH,'2011-09-23 18:03:23','2011-09-23 20:15:30')	2
WEEK	SELECT DATEDIFF(WK,'09/23/2011 15:00:00','12/11/2011 14:00:00')	12
DAY	SELECT DATEDIFF(DD,'09/23/2011 15:00:00','08/02/2011 14:00:00')	-52
DAYOFYEAR	SELECT DATEDIFF(DY,'01/01/2011 15:00:00','08/02/2011 14:00:00')	213
MONTH	SELECT DATEDIFF(MM,'11/02/2011 15:00:00','01/01/2011 14:00:00')	-10
QUARTER	SELECT DATEDIFF(QQ,'01/02/2011 15:00:00','08/01/2011 14:00:00')	2
YEAR	SELECT DATEDIFF(YY,'01/02/2011 15:00:00','01/01/2016 14:00:00')	5