SQL Server - 有条件地增加计数器

我想要做的是为连续日期范围创建分组序列。取以下样本数据：

Person|BeginDate |EndDate
A     |1/1/2015  |1/31/2015
A     |2/1/2015  |2/28/2015
A     |4/1/2015  |4/30/2015
A     |5/1/2015  |5/31/2015
B     |1/1/2015  |1/30/2015
B     |8/1/2015  |8/30/2015
B     |9/1/2015  |9/30/2015

如果当前行中的 BeginDate 距上一行中的 EndDate >1 天，则将计数器增加 1，否则分配计数器的当前值。排序如下：

Person|BeginDate |EndDate  |Sequence
A     |1/1/2015  |1/31/2015|1
A     |2/1/2015  |2/28/2015|1
A     |4/1/2015  |4/30/2015|2
A     |5/1/2015  |5/31/2015|2
B     |1/1/2015  |1/30/2015|1
B     |8/1/2015  |8/30/2015|2
B     |9/1/2015  |9/30/2015|2

为每个人进行分区和重置。

为了您的测试：

 CREATE TABLE ##SequencingTest(
 Person char(1)
,BeginDate date
,EndDate date)

INSERT INTO ##SequencingTest
VALUES
('A','1/1/2015','1/31/2015')
,('A','2/1/2015','2/28/2015')
,('A','4/1/2015','4/30/2015')
,('A','5/1/2015','5/31/2015')
,('B','1/1/2015','1/30/2015')
,('B','8/15/2015','8/31/2015')
,('B','9/1/2015','9/30/2015')

你可以这样做lag()然后是累计和：

select t.*,
       sum(flag) over (partition by person order by begindate) as sequence
from (select t.*,
             (case when datediff(day, lag(endDate) over (partition by person order by begindate), begindate) < 2
                   then 0
                   else 1
              end) as flag
      from t
     ) t;