我有一个位置表，它有"日期列"。我必须按每组位置ID查找最近的日期，例如位置ID 1的最近日期为"2022年5月31日"。在从locationID组中找到最近的日期后，我必须在最近的日期中添加14天，并将其存储在NewDate列中。并且在该位置ID组的另一行的新日期中添加+1。
我的桌子是：
id locationID Date NewDate
1 1 31 May 2022
2 1 16 May 2022
3 1 28 Apr 2021
4 2 29 Mar 2022
5 2 22 Feb 2022
6 3 14 Jun 2022
7 3 27 Oct 2021
8 4 01 Feb 2022
9 4 04 May 2022
10 4 14 Jun 2021
11 5 01 Jun 2022
12 5 29 May 2022
13 5 20 Sep 2022
14 5 11 Aug 2022
15 5 03 Aug 2022
答案如下：
例如，对于位置ID=1
id locationID Date NewDate
1 1 31 May 2022 14 Jun 2022 // Recent Date + 14 Days - 31 May + 14 Days
2 1 16 May 2022 15 Jun 2022 // Recent Date + 15 Days - 31 May + 15 Days
3 1 28 Apr 2021 16 Jun 2022 // Recent Date + 16 Days - 31 May + 16 Days
我遇到过一些类似的帖子，发现最近的日期是这样的：
SELECT L.*
FROM Locations L
INNER JOIN
(SELECT locationID, MAX(Date) AS MAXdate
FROM Locations
GROUP BY locationID) groupedL
ON L.locationID = groupedL.locationID
AND L.Date = groupedL.MAXdate
使用上面的代码，我可以找到每个位置的最近日期，但我如何添加和增加所需的天数，并将其存储到NewDate列？我是MariaDB的新手，请建议类似的帖子链接，任何参考文件或博客。我是否应该制作一些函数来执行此逻辑，并调用该函数将所需日期存储在NewDate列中？我不确定，请提出建议。非常感谢。
结果应该如下所示：
id locationID Date NewDate
1 1 31 May 2022 14 Jun 2022 // Recent Date for locationid 1 + 14 Days - 31 May + 14 Days
2 1 16 May 2022 15 Jun 2022 // Recent Date for locationid 1 + 15 Days - 31 May + 15 Days
3 1 28 Apr 2021 16 Jun 2022 // Recent Date for locationid 1 + 16 Days - 31 May + 16 Days
4 2 29 Mar 2022 12 APR 2022 // Recent Date for locationid 2 + 14 Days
5 2 22 Feb 2022 13 APR 2022 // Recent Date for locationid 2 + 15 Days
6 3 14 Jun 2022 28 JUN 2022 // Recent Date for locationid 3 + 14 Days
7 3 27 Oct 2021 29 JUN 2022 // Recent Date for locationid 3 + 15 Days
8 4 01 Feb 2022 18 MAY 2022 // Recent Date for locationid 4 + 14 Days
9 4 04 May 2022 19 MAY 2022 // Recent Date for locationid 4 + 15 Days
10 4 14 Jun 2021 20 MAY 2022 // Recent Date for locationid 4 + 16 Days
11 5 01 Jun 2022 04 OCT 2022 // Recent Date for locationid 5 + 14 Days
12 5 29 May 2022 05 OCT 2022 // Recent Date for locationid 5 + 15 Days
13 5 20 Sep 2022 06 OCT 2022 // Recent Date for locationid 5 + 16 Days
14 5 11 Aug 2022 07 OCT 2022 // Recent Date for locationid 5 + 17 Days
15 5 03 Aug 2022 08 OCT 2022 // Recent Date for locationid 5 + 18 Days
您可以使用cte:
with cte as (
select l1.*, l2.m, (select sum(l4.id < l1.id and l4.locationid = l1.locationid) from locations l4) inc from locations l1
join (select l3.locationid, max(l3.dt) m from locations l3 group by l3.locationid) l2 on l1.locationid = l2.locationid
)
select c.id, c.locationid, c.dt, c.m + interval 14 + c.inc day from cte c
您可以使用分析窗口函数，并通过加入子查询来更新原始表(适用于MariaDB(：
update t
join (
select Id,
Date_Add(First_Value(date) over(partition by locationId order by date desc),
interval (13 + row_number() over(partition by locationId order by date desc)) day
) NewDate
from t
)nd on t.id = nd.id
set t.Newdate = nd.NewDate;
请参见DB<gt；Fiddle示例