在SQL中按日期差异分组

Question

我正在使用SQL Server 2012，似乎无法弄清楚如何使用数字序列填充“ episode”列，其中仅在date（“ start_date”，“ end_date”）处增加1差异大于30天。

任何帮助将不胜感激。

Answer 1

您可以使用lag()和累计金额。但是，您已经完成了lag()，所以：

select t.*,
       sum(case when date_delta > 30 then 1 else 0 end) over (partition by id order by start_date) + 1 as episode
from t;

如果您还需要计算date_delta：

select t.*,
       sum(case when start_date > dateadd(day, 30, prev_date)
                then 1 else 0
           end) over (partition by id order by start_date) + 1 as episode
from (select t.*,
             lag(start_date) over (partition by id order by start_date) as prev_date
      from t
     ) t;