Sql server 满足条件时重置的累积公式（SQL Server）

大家好，新年快乐！ 我有一个关于累积公式的问题，如果最后一次fd之间的天数超过30天，将重置该公式。下面的例子

首先是信息有限的测试温度。我不需要在f-SDAY或最后一次fd之间的几天内得到帮助。这只是累计天数计算。我希望输出看起来像@results

DECLARE @test table(ID int, startdate date, finishdate date) 
INSERT INTO @test(ID, startdate, finishdate) VALUES

(123, '2019-12-30', '2019-12-31'),
(123, '2019-11-15', '2019-12-10'),
(123, '2019-09-12', '2019-10-10'),
(123, '2019-09-02', '2019-09-09'),
(123, '2019-08-30', '2019-09-01'),

(789, '2019-11-30', '2019-12-31'),
(789, '2019-11-15', '2019-11-17'),
(789, '2019-09-12', '2019-10-10'),
(789, '2019-09-02', '2019-09-04'),
(789, '2019-08-30', '2019-09-01')


select *
from @test





DECLARE @results TABLE(ID int, startdate date, finishdate date   ,[F-SDays] int,  DaysBetweenLastFD int, cumulativeDays int) 
INSERT INTO @results(ID, startdate, finishdate, [F-SDays], DaysBetweenLastFD, cumulativeDays) VALUES

(123, '2019-12-30', '2019-12-31', 1, 20, 26),
(123, '2019-11-15', '2019-12-10', 25, 36, 25),
(123, '2019-09-12', '2019-10-10', 28, 3, 37),
(123, '2019-09-02', '2019-09-09', 7, 1, 9),
(123, '2019-08-30', '2019-09-01', 2, 0, 2),

(789, '2019-11-30', '2019-12-31', 31, 13, 33),
(789, '2019-11-15', '2019-11-17', 2, 36, 2),
(789, '2019-09-12', '2019-10-10', 28, 8, 32),
(789, '2019-09-02', '2019-09-04', 2, 1, 4),
(789, '2019-08-30', '2019-09-01', 2, 0, 2)


select *
from @results

---

如果最后一次fd之间的天数超过30天，则设置newgroupflag。将newgroupflags相加到当前行将标识每行的当前组/序号。将每个ID和groupordinal的日期差相加将得出重置运行总数：

select *, sum(datediff(day, startdate, finishdate)) over(partition by Id, groupordinal order by startdate) as runningtotal
from
(
    select *, sum(newgroupflag) over (partition by id order by startdate) as groupordinal
    from
    (
    select *, 
    case when lag(finishdate) over(partition by id order by startdate) < dateadd(day, -30, startdate) then 1 else 0 end as newgroupflag
    from @test
    ) as gfl
) as src
order by ID, startdate;