Oracle INCREMENT fractional parts of a timestamp - oracle

Question

I have a table, which contains a timestamp. I want each row an INTERVAL apart. In my example below I am using a15 minutes interval
My first solution appears to work perfectly except that the fractional part of the timestamp is always .000000, which I expect but don't want. I'd like it to contain some other numbers.
In my second attempt I'm trying to INCREMENT the fractional part of the timestamp by .100000 the problem with this solution is if I'm creating many rows (1344) in my example, the seconds part of the timestamp gets incremented by 1 second after 10 rows are inserted. See the second solution below. I don't want that either.
Thirdly, I thought perhaps a regexp_replace solution would work where I could chop off the integer part of the second solution (keep the fractional part) and then add that to my interval. That attempt failed with an error. See third attempt below.
Is there a way I can get this to work? Where I can change the fractional part of the timestamp without it affecting the MMDDYYYY HH24:MI:SS part of the date.
Below is my code and attempts along with an example of the sample output I'm looking to generate.
Attempt #1 fractional part always .000000
CREATE TABLE t3 (
seq_num NUMBER GENERATED BY DEFAULT AS IDENTITY (START WITH 1) NOT NULL,
dt TIMESTAMP );
/
INSERT into t3 (dt)
with dt (dt, interv) as (
select timestamp '2022-01-01 00:00:00',
numtodsinterval(15,'MINUTE') from dual
union all
select dt.dt + interv, interv from dt
where dt.dt + interv < date '2022-01-15')
select dt from dt;
/
SELECT * FROM T3 ORDER BY SEQ_NUM
SEQ_NUM DT
1 01-JAN-22 12.00.00.000000 AM
2 01-JAN-22 12.15.00.000000 AM
3 01-JAN-22 12.30.00.000000 AM
4 01-JAN-22 12.45.00.000000 AM
5 01-JAN-22 01.00.00.000000 AM
6 01-JAN-22 01.15.00.000000 AM
…
...
1342 14-JAN-22 11.15.00.000000 PM
1343 14-JAN-22 11.30.00.000000 PM
1344 14-JAN-22 11.45.00.000000 PM
Attempt #2 notice the seconds change at seq_num 1355. It went from :00 to :01
TRUNCATE TABLE T3;
/
INSERT into t3 (dt)
with dt (dt, interv) as (
select timestamp '2022-01-01 00:00:00',
numtodsinterval(15,'MINUTE') +
numtodsinterval( (rownum * .100000), 'SECOND') from dual
union all
select dt.dt + interv, interv from dt
where dt.dt + interv < date '2022-01-15')
select dt from dt;
/
SELECT * FROM T3 ORDER BY SEQ_NUM
SEQ_NUM DT
1345 01-JAN-22 12.00.00.000000 AM
1346 01-JAN-22 12.15.00.100000 AM
1347 01-JAN-22 12.30.00.200000 AM
1348 01-JAN-22 12.45.00.300000 AM
1349 01-JAN-22 01.00.00.400000 AM
1350 01-JAN-22 01.15.00.500000 AM
1351 01-JAN-22 01.30.00.600000 AM
1352 01-JAN-22 01.45.00.700000 AM
1353 01-JAN-22 02.00.00.800000 AM
1354 01-JAN-22 02.15.00.900000 AM
1355 01-JAN-22 02.30.01.000000 AM
1356 01-JAN-22 02.45.01.100000 AM
…
…
Attempt #3 failed
TRUNCATE TABLE T3;
/
INSERT into t3 (dt)
with dt (dt, interv) as (
select timestamp '2022-01-01 00:00:00',
numtodsinterval(15,'MINUTE') +
regexp_replace(
numtodsinterval( (rownum * .100000), 'SECOND'), '[^.]+\.(.*)$', '0.\1') from dual
union all
select dt.dt + interv, interv from dt
where dt.dt + interv < date '2022-01-15')
select dt from dt;
/
ORA-30081: invalid data type for datetime/interval arith
Desired output
SEQ_NUM DT
1345 01-JAN-22 12.00.00.000000 AM
1346 01-JAN-22 12.15.00.100000 AM
1347 01-JAN-22 12.30.00.200000 AM
1348 01-JAN-22 12.45.00.300000 AM
1349 01-JAN-22 01.00.00.400000 AM
1350 01-JAN-22 01.15.00.500000 AM
1351 01-JAN-22 01.30.00.600000 AM
1352 01-JAN-22 01.45.00.700000 AM
1353 01-JAN-22 02.00.00.800000 AM
1354 01-JAN-22 02.15.00.900000 AM
1355 01-JAN-22 02.30.00.000000 AM
1356 01-JAN-22 02.45.00.100000 AM
1357 01-JAN-22 03.00.00.200000 AM
…
…

Answer 1

You can use:
INSERT into t3 (dt)
SELECT TIMESTAMP '2022-01-01 00:00:00'
+ (LEVEL - 1) * INTERVAL '15' MINUTE
+ MOD(LEVEL - 1, 10) * INTERVAL '0.1' SECOND
FROM DUAL
CONNECT BY
TIMESTAMP '2022-01-01 00:00:00'
+ (LEVEL - 1) * INTERVAL '15' MINUTE
+ MOD(LEVEL - 1, 10) * INTERVAL '0.1' SECOND < DATE '2022-01-15';
or:
INSERT into t3 (dt)
SELECT TIMESTAMP '2022-01-01 00:00:00'
+ NUMTODSINTERVAL((LEVEL-1)*15*60 + MOD(LEVEL-1, 10)/10, 'SECOND')
FROM DUAL
CONNECT BY
TIMESTAMP '2022-01-01 00:00:00'
+ NUMTODSINTERVAL((LEVEL-1)*15*60 + MOD(LEVEL-1, 10)/10, 'SECOND')
< DATE '2022-01-15';
Which both give the values:
SEQ_NUM
DT
1
2022-01-01 00:00:00.000000
2
2022-01-01 00:15:00.100000
3
2022-01-01 00:30:00.200000
4
2022-01-01 00:45:00.300000
5
2022-01-01 01:00:00.400000
6
2022-01-01 01:15:00.500000
7
2022-01-01 01:30:00.600000
8
2022-01-01 01:45:00.700000
9
2022-01-01 02:00:00.800000
10
2022-01-01 02:15:00.900000
11
2022-01-01 02:30:00.000000
db<>fiddle here

Answer 2

It looks like you just want to add an interval of 15 minutes and 0.1 seconds
select level seq_num,
timestamp '2022-01-01 00:00:00' +
(level-1) * interval '15' minute +
(level-1) * interval '0.1' second dt
from dual
connect by level <= 10
Here's a dbfiddle that shows it producing the output you want.