就像您的示例一样，#test是您的数据表：
;with cte1
as
(
select
ID, Date,
row_number()over(partition by ID order by Date) groupID
from #test
),
cte2
as
(
select ID, Date, Date as DateTmp, groupID, 1 as getRow from cte1 where groupID=1
union all
select
c1.ID,
c1.Date,
case when datediff(Day, c2.DateTmp, c1.Date) > 30 then c1.Date else c2.DateTmp end as DateTmp,
c1.groupID,
case when datediff(Day, c2.DateTmp, c1.Date) > 30 then 1 else 0 end as getRow
from cte1 c1
inner join cte2 c2 on c2.groupID+1=c1.groupID and c2.ID=c1.ID
)
select ID, Date from cte2 where getRow=1 order by ID, Date
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