SQL Server：确定两个日期之间的年，月，周和天

Question

在阅读了该主题并被建议使用后DateDiff。我编写的函数无法提供我想要的答案。客户现在想要完成检查清单需要多长时间。我有一个CreationDate和CompletionDate。我需要知道花了多少年，几个月，几周和几天。如果是2天，则为“ 2天”，没有年份。该功能会扣除年数，然后尝试检查月数，周数和天数。如果可用，则仅给出结果。似乎DateDiff是问题所在...或者我是无法理解的问题DateDiff。它甚至返回一个星期，日期相差4天，这没有任何意义。它应该返回两个日期内的星期数，而不用关心它的开始时间。

这是代码

ALTER FUNCTION [dbo].[DateRangeText]
    (@FromDate DATETIME, @ToDate DATETIME)
RETURNS VARCHAR(MAX)
AS
BEGIN
    DECLARE @Result AS VARCHAR(MAX);
    SET @Result = '';

    DECLARE @TmpS AS VARCHAR(MAX);
    SET @TmpS = '';

    DECLARE @Years AS INT;
    SET @Years = DATEDIFF(year, @FromDate, @ToDate);
    IF (@Years > 0)
    BEGIN
        IF (@Years = 1)
            SET @TmpS = ' Year ';
        ELSE
            SET @TmpS = ' Years ';

        SET @Result = @Result + CAST(@Years AS VARCHAR) + @TmpS;
        SET @ToDate = DATEADD(YEAR, -1 * @Years, @ToDate);
    END;

    DECLARE @Months AS INT;
    SET @Months = DATEDIFF(month, @FromDate, @ToDate);
    IF (@Months > 0)
    BEGIN
        IF (@Months = 1)
            SET @TmpS = ' Month ';
        ELSE
            SET @TmpS = ' Months ';

        SET @Result = @Result + CAST(@Months AS VARCHAR) + @TmpS;
        SET @ToDate = DATEADD(MONTH, -1 * @Months, @ToDate);
    END;

    DECLARE @Weeks AS INT;
    SET @Weeks = DATEDIFF(week, @FromDate, @ToDate);
    IF (@Weeks > 0)
    BEGIN
        IF (@Weeks = 1)
            SET @TmpS = ' Week ';
        ELSE
            SET @TmpS = ' Weeks ';

        SET @Result = @Result + CAST(@Weeks AS VARCHAR) + @TmpS;
        SET @ToDate = DATEADD(WEEK, -1 * @Weeks, @ToDate);
    END;

    DECLARE @Days AS INT;
    SET @Days = DATEDIFF(day, @FromDate, @ToDate);
    IF (@Days > 0)
    BEGIN
        IF (@Days = 1)
            SET @TmpS = ' Day ';
        ELSE
            SET @TmpS = ' Days ';

        SET @Result = @Result + CAST(@Days AS VARCHAR) + @TmpS;
        SET @ToDate = DATEADD(WEEK, -1 * @Days, @ToDate);
    END;

    IF (@Result = '')
        SET @Result = 'Same day';

    RETURN Rtrim(COALESCE(@Result,''));
END; 

Answer 1

由于使用的是函数，请考虑以下表值函数。易于单独使用或作为CROSS APPLY使用。

高效而准确，而不必担心所有其他日期的计算。

例

Select * from [dbo].[tvf-Date-Elapsed] ('1991-09-12 21:00:00.000',GetDate())

退货

Years   Months  Days    Hours   Minutes Seconds
26      7       5       13      47      11

TVF如果有兴趣

CREATE FUNCTION [dbo].[tvf-Date-Elapsed] (@D1 DateTime,@D2 DateTime)
Returns Table
Return (
    with cteBN(N)   as (Select 1 From (Values(1),(1),(1),(1),(1),(1),(1),(1),(1),(1)) N(N)),
         cteRN(R)   as (Select Row_Number() Over (Order By (Select NULL))-1 From cteBN a,cteBN b,cteBN c),
         cteYY(N,D) as (Select Max(R),Max(DateAdd(YY,R,@D1))From cteRN R Where DateAdd(YY,R,@D1)<=@D2),
         cteMM(N,D) as (Select Max(R),Max(DateAdd(MM,R,D))  From (Select Top 12 R From cteRN Order By 1) R, cteYY P Where DateAdd(MM,R,D)<=@D2),
         cteDD(N,D) as (Select Max(R),Max(DateAdd(DD,R,D))  From (Select Top 31 R From cteRN Order By 1) R, cteMM P Where DateAdd(DD,R,D)<=@D2),
         cteHH(N,D) as (Select Max(R),Max(DateAdd(HH,R,D))  From (Select Top 24 R From cteRN Order By 1) R, cteDD P Where DateAdd(HH,R,D)<=@D2),
         cteMI(N,D) as (Select Max(R),Max(DateAdd(MI,R,D))  From (Select Top 60 R From cteRN Order By 1) R, cteHH P Where DateAdd(MI,R,D)<=@D2),
         cteSS(N,D) as (Select Max(R),Max(DateAdd(SS,R,D))  From (Select Top 60 R From cteRN Order By 1) R, cteMI P Where DateAdd(SS,R,D)<=@D2)

    Select [Years]   = cteYY.N
          ,[Months]  = cteMM.N
          ,[Days]    = cteDD.N
          ,[Hours]   = cteHH.N
          ,[Minutes] = cteMI.N
          ,[Seconds] = cteSS.N
          --,[Elapsed] = Format(cteYY.N,'0000')+':'+Format(cteMM.N,'00')+':'+Format(cteDD.N,'00')+' '+Format(cteHH.N,'00')+':'+Format(cteMI.N,'00')+':'+Format(cteSS.N,'00')
     From  cteYY,cteMM,cteDD,cteHH,cteMI,cteSS
)
--Max 1000 years
--Select * from [dbo].[tvf-Date-Elapsed] ('1991-09-12 21:00:00.000',GetDate())
--Select * from [dbo].[tvf-Date-Elapsed] ('2017-01-01 20:30:15','2018-02-05 22:58:35')