Generate a random NUMBER of timestamps for each date INTERVAL - sql

Question

Below I am generating rows every 15 minutes from a start time to an end time.
Within the first start and END time
25-JAN-2023 09:00:00.000000
25-JAN-2023 09:15:00.000000
I want to pass these values to the function random_timestamp and generate a random number of timestamps (ie 3-10), which fall between the two timestamps.
I get the next group of times
25-JAN-2023 09:15:00.000000
25-JAN-2023 09:30:00.000000
Call the random_timestamp function again to generate a random number (ie 3-10) of timestamps for that period
I repeat the process until I hit the last set of times
25-JAN-2023 11:45:00.000000
25-JAN-2023 12:00:00.000000
I saw something about a lag function and I think that may help but I'm unsure how to implement it into my example where I need to pass two values to my function.
I know I need to put this logic in my code
SELECT random_timestamp(
TIMESTAMP '2023-01-25 11:45:00',
TIMESTAMP '2023-01-25 12:00:00') from dual connect by level <= ( select dbms_random.value ( 3, 10 ) n from dual )
in place of
select dt from dt;
Below is my test CASE and an example of the desired output. Any help would be appreciated.
ALTER SESSION SET NLS_TIMESTAMP_FORMAT = 'DD-MON-YYYY HH24:MI:SS.FF';
with dt (dt, interv) as (
select TIMESTAMP '2023-01-25 09:00:00',
numtodsinterval(15,'MINUTE') from dual
union all
select dt.dt + interv, interv from dt
where dt.dt + interv <= TIMESTAMP '2023-01-25 12:00:00')
select dt from dt;
/
DT
25-JAN-2023 09:00:00.000000
25-JAN-2023 09:15:00.000000
25-JAN-2023 09:30:00.000000
25-JAN-2023 09:45:00.000000
25-JAN-2023 10:00:00.000000
25-JAN-2023 10:15:00.000000
25-JAN-2023 10:30:00.000000
25-JAN-2023 10:45:00.000000
25-JAN-2023 11:00:00.000000
25-JAN-2023 11:15:00.000000
25-JAN-2023 11:30:00.000000
25-JAN-2023 11:45:00.000000
25-JAN-2023 12:00:00.000000
CREATE OR REPLACE FUNCTION random_timestamp(
p_from IN TIMESTAMP,
p_to IN TIMESTAMP,
p_fraction IN VARCHAR2 DEFAULT 'Y'
) RETURN TIMESTAMP
IS
return_val_y TIMESTAMP(9) := p_from + dbms_random.value() * (p_to - p_from);
return_val_n TIMESTAMP(0) := return_val_y;
BEGIN
RETURN CASE
WHEN p_fraction LIKE 'Y%' OR p_fraction LIKE 'y%'
THEN return_val_y
ELSE return_val_n
END;
END random_timestamp;
/
The end result should be something like this below. Note I put an empty line between each call to the function to show a different amount of rows for each call to my function.
25-JAN-2023 09:04:42.917984
25-JAN-2023 09:04:38.082448
25-JAN-2023 09:11:43.368529
25-JAN-2023 09:04:56.513339
25-JAN-2023 09:10:21.592329
25-JAN-2023 09:06:56.241198
25-JAN-2023 09:03:02.853214
25-JAN-2023 09:18:43.151379
25-JAN-2023 09:16:10.342814
25-JAN-2023 09:21:38.186374
…
…
…
25-JAN-2023 11:52:25.095462
25-JAN-2023 11:50:43.687866
25-JAN-2023 11:58:15.107269
25-JAN-2023 11:57:21.549818
25-JAN-2023 11:50:10.750542

Answer 1

You can use:
WITH dt (dt, interv, rnd) AS (
SELECT TIMESTAMP '2023-01-25 09:00:00',
INTERVAL '15' MINUTE,
FLOOR(DBMS_RANDOM.VALUE(3,11))
FROM DUAL
UNION ALL
SELECT dt.dt + interv,
interv,
FLOOR(DBMS_RANDOM.VALUE(3,11))
FROM dt
WHERE dt.dt + interv <= TIMESTAMP '2023-01-25 12:00:00'
)
SELECT random_timestamp(dt, dt + INTERVAL '15' MINUTE) AS dt
FROM dt
CROSS APPLY (
SELECT LEVEL AS lvl
FROM DUAL
CONNECT BY LEVEL <= rnd
)
ORDER BY dt;
fiddle

Answer 2

You can use DBMS_RANDOM function to generate a value between 90 and 300 seconds (that give you 3-10 rows per 15 minutes) to be added to your timestamp.
WITH dt (dt) AS (
SELECT TIMESTAMP '2023-01-25 09:00:00'
+ NUMTODSINTERVAL(DBMS_RANDOM.VALUE(90, 300),'SECOND') FROM dual
UNION ALL
SELECT dt.dt + NUMTODSINTERVAL(DBMS_RANDOM.VALUE(90, 300),'SECOND')
FROM dt
WHERE dt.dt + NUMTODSINTERVAL(15,'MINUTE') <= TIMESTAMP '2023-01-25 12:00:00'
)
SELECT dt FROM dt;
Check the demo here.

Answer 3

Get the difference in seconds between the from/to by casting to a date (easier to work with than intervals), then add in any fractional piece. Generate a random number between 0 and that difference, then add it back as seconds to the from date.
CREATE OR REPLACE FUNCTION random_timestamp (
p_from IN TIMESTAMP,
p_to IN TIMESTAMP
) RETURN TIMESTAMP
AS
var_diff number;
BEGIN
var_diff := ((CAST(p_to AS date) - CAST(p_from AS date)) * 86400) + (EXTRACT(SECOND FROM p_to) - EXTRACT(SECOND FROM p_from));
RETURN NUMTODSINTERVAL(dbms_random.value(0,var_diff),'SECOND') + p_from;
END;
To generate 15-minute intervals, just multiply level by 15 and add it as a minute interval to your starting point:
SELECT random_timestamp(TIMESTAMP '2023-01-25 11:45:00' + NUMTODSINTERVAL(level*15,'MINUTE'),
TIMESTAMP '2023-01-25 12:00:00' + NUMTODSINTERVAL(level*15,'MINUTE'))
from dual connect by level <= 5