问如何为Sql Server行中的一系列常量更改生成序列号

EN

select t.*,
       (case when sender = 'vendor'
             then datediff(second,
                           min(date) over (partition by grp),
                           max(date) over (partition by grp)
                          ) / (24 * 60 * 60.0)
        end) as diff
from (select t.*,
             sum(case when sender = 'Vendor' then 1 else 0 end) over (order by id desc) as grp
      from t
     ) t;