在SQL中，如何根据开始日期和经过的天数计算一年中的天数

Question

如果我有一个开始日期和已经失效的天数，那么计算每年的天数是什么？

例如，日期（ymd）2013-01-01和已过去的天数为1000。

我希望结果看起来像这样

2013 = 365

2014 = 365

2015 = 270

这可以写成像datediff这样的函数吗？

我尝试过使用日历表，但当然，链接到这只会给我2013 = 1000

我的日历表看起来像这样。

DATE_ID  | DATE       | CALENDAR_YEAR | FINANCIAL_YEAR
-----------------------------------------------
20130101 | 2013-01-01 | 2013          | 2013/14

这就是我尝试过的。

选择

D.FISCAL_YEAR，SUM（[DAYS]）AS NUMBER_OF_DAYS

来自[dbo]。[FACT] F.

LEFT JOIN [dbo]。[DIM_DATE] D ON D.DATE_ID = F.DATE_ID

通过...分组

D.FISCAL_YEAR

结果是。

FISCAL_YEAR | NUMBER_OF_DAYS
----------------------------
2013/14     |2820 
2014/15     |6635 
2015/16     |2409

Answer 1

我个人会建立一个计数表来做到这一点。 构建完成后，您可以轻松获取每个日期并计算每年的天数：

DECLARE @YMD date = '20130101',
        @Lapsed int = 1000;

--Build a Tally table
WITH N AS(
    SELECT N
    FROM (VALUES(NULL),(NULL),(NULL),(NULL),(NULL),(NULL),(NULL),(NULL),(NULL),(NULL)) N(N)),
Tally AS(
    SELECT ROW_NUMBER() OVER (ORDER BY (SELECT NULL)) -1 AS I
    FROM N N1, N N2, N N3, N N4), --10,000 should be enough
--Build the dates table
Dates AS(
    SELECT DATEADD(DAY, T.I, @YMD) AS CalendarDate
    FROM Tally T
    WHERE T.I <= @Lapsed - 1)
--And count the days
SELECT DATEPART(YEAR, CalendarDate) AS Year,
       COUNT(CalendarDate) AS Days
FROM Dates D
GROUP BY DATEPART(YEAR, CalendarDate);

作为一个功能：

CREATE FUNCTION CountDays (@YMD date, @Lapsed int)
RETURNS table 
AS RETURN

    --Build a Tally table
    WITH N AS(
        SELECT N
        FROM (VALUES(NULL),(NULL),(NULL),(NULL),(NULL),(NULL),(NULL),(NULL),(NULL),(NULL)) N(N)),
    Tally AS(
        SELECT ROW_NUMBER() OVER (ORDER BY (SELECT NULL)) -1 AS I
        FROM N N1, N N2, N N3, N N4), --10,000 should be enough
    --Build the dates table
    Dates AS(
        SELECT DATEADD(DAY, T.I, @YMD) AS CalendarDate
        FROM Tally T
        WHERE T.I <= @Lapsed - 1)
    --And count the days
    SELECT DATEPART(YEAR, CalendarDate) AS Year,
           COUNT(CalendarDate) AS Days
    FROM Dates D
    GROUP BY DATEPART(YEAR, CalendarDate);

GO

SELECT *
FROM (VALUES('20130101',1000),
            ('20150501',755))V(YMD, Lapsed)
     CROSS APPLY dbo.CountDays(V.YMD,V.Lapsed) CD;

Answer 2

一种方法是递归CTE：

with dates as (
      select v.d, 1000 - datediff(day, v.d, dateadd(year, 1, v.d)) as days
      from (values (datefromparts(2013, 1, 1))) v(d)
      union all
      select dateadd(year, 1, d), days - datediff(day, d, dateadd(year, 1, d)) 
      from dates
      where days > 0
     )
select d,
       (case when days > 0 then datediff(day, d, dateadd(year, 1, d))
             else datediff(day, d, dateadd(year, 1, d)) + days
        end)
from dates;

这是一个db <>小提琴。