Oracle 18c

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create table t (dat date, amt integer);
insert into t values (date'2023-04-02', 100);
1 rows affected

insert into t values (date'2023-04-03', 102);
1 rows affected

insert into t values (date'2023-04-06', 200);
1 rows affected

with dates (dat) as (
  select min(dat) from t
  union all
  select dat + interval '1' day from dates
  where dat <= (select max(dat) from t)
  )
select * from dates
  


DAT


02-APR-23

03-APR-23

04-APR-23

05-APR-23

06-APR-23

07-APR-23


with dates (dat) as (
  select min(dat) from t
  union all
  select dat + interval '1' day from dates
  where dat < (select max(dat) from t)
  )
select d.dat, last_value(t.amt) ignore nulls over (order by d.dat) amt
from dates d
left join t on d.dat = t.dat
order by d.dat


DAT
AMT


02-APR-23
100

03-APR-23
102

04-APR-23
102

05-APR-23
102

06-APR-23
200

DAT	AMT
02-APR-23	100
03-APR-23	102
04-APR-23	102
05-APR-23	102
06-APR-23	200