一种方法使用 not exists :

select min(eventtime)
from t
where not exists (select 1
                  from t t2
                  where t2.eventtime > t.eventtime and t2.DOCUMENTTYPE <> 'XX'
                 );

另一个有趣的方法是使用窗口函数：

select min(eventtime)
from (select t.*,
             row_number() over (order by eventtime desc) as seqnum,
             row_number() over (partition by documenttype order by eventtime desc) as seqnum_dt
      from t
     ) t
where documenttype = 'XX' and
      seqnum = seqnum_dt;

这使用了这样一个事实，即 'XX' 仅基于 eventtime 或者基于 eventtime 当按分区时 dcoumenttype .

这将返回最后一组accept/xx行的第一行：

WITH flag_actions AS
 (
   SELECT t.*
     -- used to filter in next step: previous row was not Accept/XX = 1st row of group
     ,Lag(CASE WHEN ACTION = 'Accept' AND DOCUMENTTYPE = 'XX' THEN 0 ELSE 1 END, 1, 1)
      Over (PARTITION BY ???
            ORDER BY EVENTTIME) AS flag
   FROM t
 )
,find_latest AS
 (
   SELECT flag_actions.*
      -- used to filter in next step
     ,Row_Number()
      Over (PARTITION BY ??? 
            ORDER BY EVENTTIME DESC) AS rn
   FROM flag_actions
   WHERE ACTION = 'Accept' -- last row for each group of Accept/XX rows
     AND DOCUMENTTYPE = 'XX'
     AND flag = 1
 )
SELECT * 
FROM find_latest
WHERE rn = 1

如果没有嵌套的olap函数，我怀疑你能得到这样的结果。