SQL服务器 DATEDIFF() 函数

返回两个日期值之间的差值（以年为单位）：

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

定义和用法

DATEDIFF() 函数返回两个日期之间的差异。

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

工作于：	SQL Server（从 2008 年开始）、Azure SQL 数据库、Azure SQL 数据仓库、并行数据仓库