Oracle 21c

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create table mytable (rtc_timestamp, rtc_event_order_seq) as
select timestamp '2022-01-01 12:13:14', 1 from dual union all
select timestamp '2022-01-01 12:13:14', 2 from dual
2 rows affected

select TO_TIMESTAMP(to_char(RTC_TIMESTAMP, 'yyyy-mm-dd hh24:mi:ss') || ',' || lpad(rtc_event_order_seq, 3, '0'), 'YYYY-MM-DD HH24:MI:SS,FF3') AS TIME_STAMP,
TO_TIMESTAMP(to_char((Lead(RTC_TIMESTAMP,1)over(order by RTC_TIMESTAMP)), 'yyyy-mm-dd hh24:mi:ss') || ',' || lpad(rtc_event_order_seq, 3, '0'), 'YYYY-MM-DD HH24:MI:SS,FF3') AS NEXT_TIMESTAMP
from mytable
ORA-01841: (full) year must be between -4713 and +9999, and not be 0

select to_char(RTC_TIMESTAMP, 'yyyy-mm-dd hh24:mi:ss') || ',' || lpad(rtc_event_order_seq, 3, '0') AS TIME_STAMP,
to_char((Lead(RTC_TIMESTAMP,1)over(order by RTC_TIMESTAMP)), 'yyyy-mm-dd hh24:mi:ss') || ',' || lpad(rtc_event_order_seq, 3, '0') AS NEXT_TIMESTAMP
from mytable


TIME_STAMP
NEXT_TIMESTAMP


2022-01-01 12:13:14,002
2022-01-01 12:13:14,002

2022-01-01 12:13:14,001
,001


select to_char(RTC_TIMESTAMP, 'yyyy-mm-dd hh24:mi:ss') || ',' || lpad(rtc_event_order_seq, 3, '0') AS TIME_STAMP,
to_char((Lead(RTC_TIMESTAMP,1)over(order by RTC_TIMESTAMP)), 'yyyy-mm-dd hh24:mi:ss') || ',' || lpad(Lead(rtc_event_order_seq,1)over(order by RTC_TIMESTAMP), 3, '0') AS NEXT_TIMESTAMP
from mytable


TIME_STAMP
NEXT_TIMESTAMP


2022-01-01 12:13:14,002
2022-01-01 12:13:14,001

2022-01-01 12:13:14,001
,


select TO_TIMESTAMP(to_char(RTC_TIMESTAMP, 'yyyy-mm-dd hh24:mi:ss') || ',' || lpad(rtc_event_order_seq, 3, '0'), 'YYYY-MM-DD HH24:MI:SS,FF3') AS TIME_STAMP,
TO_TIMESTAMP(to_char((Lead(RTC_TIMESTAMP,1)over(order by RTC_TIMESTAMP)), 'yyyy-mm-dd hh24:mi:ss') || ',' || lpad(Lead(rtc_event_order_seq,1)over(order by RTC_TIMESTAMP), 3, '0'), 'YYYY-MM-DD HH24:MI:SS,FF3') AS NEXT_TIMESTAMP
from mytable
ORA-01841: (full) year must be between -4713 and +9999, and not be 0

select TO_TIMESTAMP(to_char(RTC_TIMESTAMP, 'yyyy-mm-dd hh24:mi:ss') || ',' || lpad(rtc_event_order_seq, 3, '0'), 'YYYY-MM-DD HH24:MI:SS,FF3') AS TIME_STAMP,
  case when Lead(RTC_TIMESTAMP,1)over(order by RTC_TIMESTAMP) is not null then
    TO_TIMESTAMP(to_char((Lead(RTC_TIMESTAMP,1)over(order by RTC_TIMESTAMP)), 'yyyy-mm-dd hh24:mi:ss')
      || ',' || lpad(Lead(rtc_event_order_seq,1)over(order by RTC_TIMESTAMP), 3, '0'), 'YYYY-MM-DD HH24:MI:SS,FF3')
    end AS NEXT_TIMESTAMP
from mytable


TIME_STAMP
NEXT_TIMESTAMP


01-JAN-22 12.13.14.002000000
01-JAN-22 12.13.14.001000000

01-JAN-22 12.13.14.001000000
null


select RTC_TIMESTAMP + (rtc_event_order_seq * interval '0.001' second) AS TIME_STAMP,
  case when Lead(RTC_TIMESTAMP, 1) over (order by RTC_TIMESTAMP) is not null then
    Lead(RTC_TIMESTAMP, 1) over (order by RTC_TIMESTAMP)
      + (Lead(rtc_event_order_seq, 1) over (order by RTC_TIMESTAMP) * interval '0.001' second)
    end AS NEXT_TIMESTAMP
from mytable


TIME_STAMP
NEXT_TIMESTAMP


01-JAN-22 12.13.14.002000000
01-JAN-22 12.13.14.001000000

01-JAN-22 12.13.14.001000000
null
TIME_STAMP	NEXT_TIMESTAMP
2022-01-01 12:13:14,002	2022-01-01 12:13:14,002
2022-01-01 12:13:14,001	,001
TIME_STAMP	NEXT_TIMESTAMP
01-JAN-22 12.13.14.002000000	01-JAN-22 12.13.14.001000000
01-JAN-22 12.13.14.001000000	null