问题描述

我有一些数据存储在这样的表中:

I have some data stored in a table like this:

VacationId VacationDate VacationDuration_Hr
1          2018/01/24      4
2          2018/03/21      60
3          2018/08/16      33
4          2018/12/01      8

我希望能够将较长的时间段分解为几个较短的时间段，最大长度为 24 小时，如下所示:

I'd like to be able to break down the longer time periods into several shorter ones with the max length of 24hr like this:

VacationDate VacationDuration_Hr
2018/01/24      4
2018/03/21      24
2018/03/22      24
2018/03/23      12
2018/08/16      24
2018/08/17      9
2018/12/01      8

没有游标有什么技巧吗?提前致谢

Is there a trick to do it without cursors? Thanks In advance

推荐答案

我在这里使用的方法是创建额外行的 Tally Table.我 JOIN 到计数表上，其中小时数/24(整数数学很有用)大于计数值，然后可以使用它来计算小时数.

The method I have used here is a Tally Table to create extra rows. I JOIN onto the tally table where the number of hours / 24 (integer maths is useful) is greater than the tally number, and then can use that to calculate the hours.

WITH YourTable AS(
    SELECT *
    FROM (VALUES(1,CONVERT(date,'2018/01/24',111),4 ),
                (2,CONVERT(date,'2018/03/21',111),40),
                (3,CONVERT(date,'2018/08/16',111),33),
                (4,CONVERT(date,'2018/12/01',111),8 ),
                (5,CONVERT(date,'2018/12/17',111),56 ),
                (6,CONVERT(date,'2018/12/17',111),24 ))V(VacationID,VacationDate,VacationDuration_Hr)),
--Solution
N AS(
    SELECT N
    FROM (VALUES(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) -- 25 days, add more for more days
SELECT YT.VacationID,
       DATEADD(DAY, T.I, YT.VacationDate) AS VacationDate,
       CASE WHEN VacationDuration_Hr - (T.I * 24) > 24 THEN 24 ELSE YT.VacationDuration_Hr - (T.I * 24) END AS VacationDuration_Hr
FROM YourTable YT
     JOIN Tally T ON (YT.VacationDuration_Hr -1) / 24 >= T.I
ORDER BY YT.VacationID,
         T.I;

您可以也可以在这里使用 rCTE，但是，我倾向于避免使用 rCTE；特别是当我不知道 VacationDuration_Hr 的值的上限可能是什么时.如果它很大，则可能会对性能产生一些不利影响，并且 Tally 的性能将明显优于 rCTE 的 RBAR 性质.

You could also use an rCTE here instead, however, I tend to avoid those for things like this; especially when I have no context of what the upper limit to the value of VacationDuration_Hr could be. if it is large it could have some nasty performance implications and a Tally will significantly out perform the RBAR nature of an rCTE.

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