Question

我希望在指定日期之前的星期二（或任何特定的一周）。以下是星期二的示例输入和预期输出：

CREATE TABLE #temp(testdate DATETIME);
INSERT INTO  #temp(testdate) VALUES
    ('2015-10-06 01:15'), -- Tue -> Tue 2015-10-06 00:00
    ('2015-10-07 04:30'), -- Wed -> Tue 2015-10-06 00:00
    ('2015-10-08 00:30'), -- Thu -> Tue 2015-10-06 00:00
    ('2015-10-09 21:00'), -- Fri -> Tue 2015-10-06 00:00
    ('2015-10-10 19:00'), -- Sat -> Tue 2015-10-06 00:00
    ('2015-10-11 01:15'), -- Sun -> Tue 2015-10-06 00:00
    ('2015-10-12 13:00'), -- Mon -> Tue 2015-10-06 00:00

    ('2015-10-13 18:45'), -- Tue -> Tue 2015-10-13 00:00
    ('2015-10-14 12:15'), -- Wed -> Tue 2015-10-13 00:00
    ('2015-10-15 10:45'), -- Thu -> Tue 2015-10-13 00:00
    ('2015-10-16 04:30'), -- Fri -> Tue 2015-10-13 00:00
    ('2015-10-17 12:15'), -- Sat -> Tue 2015-10-13 00:00
    ('2015-10-18 00:30'), -- Sun -> Tue 2015-10-13 00:00
    ('2015-10-19 10:45'), -- Mon -> Tue 2015-10-13 00:00

    ('2015-10-20 01:15'), -- Tue -> Tue 2015-10-20 00:00
    ('2015-10-21 23:45'), -- Wed -> Tue 2015-10-20 00:00
    ('2015-10-22 21:00'), -- Thu -> Tue 2015-10-20 00:00
    ('2015-10-23 18:45'), -- Fri -> Tue 2015-10-20 00:00
    ('2015-10-24 06:45'), -- Sat -> Tue 2015-10-20 00:00
    ('2015-10-25 06:45'), -- Sun -> Tue 2015-10-20 00:00
    ('2015-10-26 04:30'); -- Mon -> Tue 2015-10-20 00:00

DECLARE @clampday AS INT = 3; -- Tuesday
SELECT -- DATEADD/DATEPART/@clampday/???

使用T-SQL获取上周二（或任何一周）的最合适方式是什么？

Answer 1

我希望这会对你有所帮助

SELECT DATEADD(day,- (DATEPART(dw, testdate) + @@DATEFIRST - 3) % 7,testdate) AS Saturday  
from #temp

OR

SELECT DATENAME(weekday,DATEADD(day,- (DATEPART(dw, testdate) + @@DATEFIRST - 3) % 7,testdate)) +'  '+ 
        CONVERT(nvarchar,DATEADD(day,- (DATEPART(dw, testdate) + @@DATEFIRST - 3) % 7,testdate),101) AS Saturday
from @temp

OUTPUT将在下面的合成中

Saturday
Tuesday  10/06/2015

备注：整个查询只是组合和计算DATEFIRST，DATEPART和DATEADD来操纵时间

Answer 2

您可以使用DATEPART使用获取周数，然后在以下内容中使用CASE语句：

SELECT
    testdate,
    CASE DATEPART(dw,testdate)  WHEN 1 THEN DATEADD(dd,-5,testdate) 
                                WHEN 2 THEN DATEADD(dd,-6,testdate) 
                                WHEN 3 THEN DATEADD(dd, 0,testdate) 
                                WHEN 4 THEN DATEADD(dd,-1,testdate) 
                                WHEN 5 THEN DATEADD(dd,-2,testdate) 
                                WHEN 6 THEN DATEADD(dd,-3,testdate) 
                                WHEN 7 THEN DATEADD(dd,-4,testdate)                                     
    END
FROM #temp

根据@jpw评论，你必须在下面将DATEFIRST设置为7（默认值）：

SET DATEFIRST 7

Answer 3

CREATE PROC FIND_TUESDAY_DATE
(
 @MYDATE DATE
)
AS 
BEGIN
    SELECT CASE 
            WHEN DATENAME(DW,CAST(DATEADD(DAY,0,@MYDATE) AS DATE)) = 'Tuesday' OR DATENAME(DW,CAST(DATEADD(DAY,-7,@MYDATE) AS DATE))  = 'Tuesday' 
            THEN CAST(DATEADD(DAY,-7,@MYDATE) AS DATE)
            WHEN DATENAME(DW,CAST(DATEADD(DAY,-1,@MYDATE) AS DATE) ) = 'Tuesday' THEN CAST(DATEADD(DAY,-1,@MYDATE) AS DATE)
            WHEN DATENAME(DW,CAST(DATEADD(DAY,-2,@MYDATE) AS DATE) ) = 'Tuesday' THEN CAST(DATEADD(DAY,-2,@MYDATE) AS DATE)
            WHEN DATENAME(DW,CAST(DATEADD(DAY,-3,@MYDATE) AS DATE) ) = 'Tuesday' THEN CAST(DATEADD(DAY,-3,@MYDATE) AS DATE)
            WHEN DATENAME(DW,CAST(DATEADD(DAY,-4,@MYDATE) AS DATE) ) = 'Tuesday' THEN CAST(DATEADD(DAY,-4,@MYDATE) AS DATE)
            WHEN DATENAME(DW,CAST(DATEADD(DAY,-5,@MYDATE) AS DATE) ) = 'Tuesday' THEN CAST(DATEADD(DAY,-5,@MYDATE) AS DATE)
            WHEN DATENAME(DW,CAST(DATEADD(DAY,-6,@MYDATE) AS DATE) ) = 'Tuesday' THEN CAST(DATEADD(DAY,-6,@MYDATE) AS DATE)
        END
END
GO

Answer 4

最有效的方法是使用DATEADD和DATEDIFF：

这是您需要的所有代码，它也适用于其他工作日

DECLARE @daystoadd int = 1 -- tuesday


SELECT DATEADD(week, datediff(d, @daystoadd, testdate) / 7, @daystoadd)
FROM #temp

Answer 5

回答一些细节是否仍然有帮助：

declare @given_date datetime = '2015-10-15 00:30'
declare @required_weekday int = 1 -- tuesday

select dateadd(week, datediff(week, 0, @given_date), @required_weekday)

说明：

datediff(week, 0, @given_date)：返回在 1900-01-01 和给定日期

_number_of_weeks

dateadd(week, number_of_weeks, @required_weekday)：将计算出的 number_of_weeks 和给定的 required_weekday 添加到初始日历日期 1900-01-01

获取指定日期的上周二（或任何特定日期）

5 个答案: