DATEDIFF (Transact-SQL)

dataDiff 多用于获取指定时间间隔内的数据集，如：

                select
                   count(1) as col2
                from
                   ComplaintMain cm
                where
                   DateDiff(dd,cm.CreatedOn,getDate())<=7 
                 and
                   cm.HandlingBy=" + (int)HandlingBy.MemberCD + @"
                 and 
                   cm.CState=" + (int)ComplaintState.Successfully + ";";

上面的query是获取一周内条件数据；

函数方法：

DATEDIFF ( datepart , startdate , enddate )

datepart参数：

datepart	Abbreviations
year	yy, yyyy
quarter	qq, q
month	mm, m
dayofyear	dy, y
day	dd, d
week	wk, ww
hour	hh
minute	mi, n
second	ss, s
millisecond	ms
microsecond	mcs
nanosecond	ns

demo:

SELECT DATEDIFF(year, '2005-12-31 23:59:59.9999999'
, '2006-01-01 00:00:00.0000000');
SELECT DATEDIFF(quarter, '2005-12-31 23:59:59.9999999'
, '2006-01-01 00:00:00.0000000');
SELECT DATEDIFF(month, '2005-12-31 23:59:59.9999999'
, '2006-01-01 00:00:00.0000000');
SELECT DATEDIFF(dayofyear, '2005-12-31 23:59:59.9999999'
, '2006-01-01 00:00:00.0000000');
SELECT DATEDIFF(day, '2005-12-31 23:59:59.9999999'
, '2006-01-01 00:00:00.0000000');
SELECT DATEDIFF(week, '2005-12-31 23:59:59.9999999'
, '2006-01-01 00:00:00.0000000');
SELECT DATEDIFF(hour, '2005-12-31 23:59:59.9999999'
, '2006-01-01 00:00:00.0000000');
SELECT DATEDIFF(minute, '2005-12-31 23:59:59.9999999'
, '2006-01-01 00:00:00.0000000');
SELECT DATEDIFF(second, '2005-12-31 23:59:59.9999999'
, '2006-01-01 00:00:00.0000000');
SELECT DATEDIFF(millisecond, '2005-12-31 23:59:59.9999999'
, '2006-01-01 00:00:00.0000000');

例子：

CREATE TABLE dbo.Duration
    (
    startDate datetime2
    ,endDate datetime2
    );
INSERT INTO dbo.Duration(startDate,endDate)
    VALUES('2007-05-06 12:10:09','2007-05-07 12:10:09');
SELECT DATEDIFF(day,startDate,endDate) AS 'Duration'
FROM dbo.Duration;
-- Returns: 1