Oracle 11g Release 2

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with heats( start_date, stop_date, sample_date, sample_value ) as
(
 select timestamp'2019-11-11 08:00:00', timestamp'2019-11-11 09:00:00', timestamp'2019-11-11 08:10:00',10 from dual union all
 select timestamp'2019-11-11 08:00:00', timestamp'2019-11-11 09:00:00', timestamp'2019-11-11 08:14:00',20 from dual union all
 select timestamp'2019-11-11 08:00:00', timestamp'2019-11-11 09:00:00', timestamp'2019-11-11 08:20:00',15 from dual union all
 select timestamp'2019-11-11 08:00:00', timestamp'2019-11-11 09:00:00', timestamp'2019-11-11 08:40:00',10 from dual union all
 select timestamp'2019-11-11 08:00:00', timestamp'2019-11-11 09:00:00', timestamp'2019-11-11 08:50:00',21 from dual union all
 select timestamp'2019-11-11 08:00:00', timestamp'2019-11-11 09:00:00', timestamp'2019-11-11 08:55:00',20 from dual 
), t as
(
 select start_date + 
        level * ( stop_date - start_date ) 
               /( ( extract(hour from (stop_date - start_date))*60+
                      extract(minute from (stop_date - start_date)) )
                     / 15  )  as split_date, 
        start_date, stop_date, sample_date, sample_value, level as lvl
   from heats
connect by level <= ( extract(hour from (stop_date - start_date))*60+
                      extract(minute from (stop_date - start_date)) )
                     / 15   
   and prior sys_guid() is not null
   and prior sample_date = sample_date
), t2 as
(
select row_number() over (partition by split_date order by sample_date desc) as rn,
       t.*
  from t     
 where sample_date < split_date   
)
select start_date, stop_date, 
       max( case when lvl = 1 then sample_value end ) as part1,
       max( case when lvl = 2 then sample_value end ) as part2,
       max( case when lvl = 3 then sample_value end ) as part3,
       max( case when lvl = 4 then sample_value end ) as part4
  from t2
 where rn = 1 
 group by start_date, stop_date
 order by rn desc

START_DATE	STOP_DATE	PART1	PART2	PART3	PART4
11-NOV-19 08.00.00.000000000 AM	11-NOV-19 09.00.00.000000000 AM	20	15	10	20