Oracle 18c

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create table mytable (ROW_ID Number(5), POLICY_ID Number(5), 
                      CHANGE_NO Number(5), STATUS VARCHAR(50), CHANGE_DATE DATE);
insert all
into mytable values (  81, 1, 1, 'A', date '2018-01-01')
into  mytable values (  95, 1, 2, 'A', date '2018-01-02')
into mytable values ( 100, 1, 3, 'B', date '2018-01-03')
 into mytable values ( 150, 1, 4, 'C', date '2018-01-04')
 into mytable values ( 165, 1, 5, 'A', date '2018-01-05')
 into mytable values ( 175, 1, 6, 'A', date '2018-01-06')
 into mytable values ( 599, 2, 1, 'S', date '2018-01-11')
 into mytable values ( 602, 2, 2, 'S', date '2018-01-12')
 into mytable values ( 611, 2, 3, 'S', date '2018-01-13')
 into mytable values ( 629, 2, 4, 'T', date '2018-01-14')
 into mytable values ( 720, 2, 5, 'U', date '2018-01-15')
 into mytable values ( 790, 2, 6, 'S', date '2018-01-16')
 into mytable values ( 812, 2, 7, 'S', date '2018-01-17')
into mytable values ( 825, 2, 8, 'S', date '2018-01-18')
--into mytable values(1000,3,1,'A', date '2018-01-01')
--into mytable values(1000,3,2,'A', date '2018-01-02')
--into mytable values(1000,3,3,'C', date '2018-01-03')
SELECT *
FROM dual
14 rows affected

-- Gordon's approach
select t.*
from (select t.*,
             row_number() over (partition by policy_id order by change_date asc) as seqnum
      from  mytable t
      where not exists (select 1
                        from mytable t2
                        where t2.policy_id = t.policy_id and
                              t2.status <> t.status and
                              t2.change_date > t.change_date
                       )
     ) t
where seqnum = 1;


ROW_ID
POLICY_ID
CHANGE_NO
STATUS
CHANGE_DATE
SEQNUM


165
1
5
A
05-JAN-18
1

790
2
6
S
16-JAN-18
1


SELECT ROW_ID, POLICY_ID, CHANGE_NO, STATUS, CHANGE_DATE
FROM mytable
MATCH_RECOGNIZE (
  PARTITION BY POLICY_ID
  ORDER BY CHANGE_DATE
  MEASURES MATCH_NUMBER() m,FIRST(R.ROW_ID) r
  ALL ROWS PER MATCH
  PATTERN (R+)
  DEFINE R AS STATUS=NEXT(STATUS)
) MR
WHERE ROW_ID = R
ORDER BY ROW_NUMBER() OVER(PARTITION BY POLICY_ID ORDER BY M DESC)
FETCH FIRST 1 ROW WITH TIES


ROW_ID
POLICY_ID
CHANGE_NO
STATUS
CHANGE_DATE


165
1
5
A
05-JAN-18

790
2
6
S
16-JAN-18