SQL Server DATEDIFF() Function

Return the difference between two date values, in years:

SELECT DATEDIFF(year, '2017/08/25', '2011/08/25') AS DateDiff;

Definition and Usage

The DATEDIFF() function returns the difference between two dates.

DATEDIFF(interval, date1, date2)

Parameter	Description
interval	Required. The part to return. Can be one of the following values: year, yyyy, yy = Year quarter, qq, q = Quarter month, mm, m = month dayofyear = Day of the year day, dy, y = Day week, ww, wk = Week weekday, dw, w = Weekday hour, hh = hour minute, mi, n = Minute second, ss, s = Second millisecond, ms = Millisecond
date1, date2	Required. The two dates to calculate the difference between

Works in:	SQL Server (starting with 2008), Azure SQL Database, Azure SQL Data Warehouse, Parallel Data Warehouse

Return the difference between two date values, in months:

SELECT DATEDIFF(month, '2017/08/25', '2011/08/25') AS DateDiff;

Return the difference between two date values, in hours:

SELECT DATEDIFF(hour, '2017/08/25 07:00', '2017/08/25 12:45') AS DateDiff;