datediff function for dates or timestamps - oracle

Question

I have a function that calculates the difference between 2 dates or timestamps which is working fine.
Is there a way to modify the function to display the fractional part of the TIMESTAMP in the difference as part of the result. I want both cases to be handled in the same function if possible.
CREATE OR REPLACE FUNCTION datediff (p_from date, p_to date)
return varchar2 is
l_years PLS_INTEGER;
l_from DATE;
l_interval interval day(3) to second(0);
begin
l_years := TRUNC(MONTHS_BETWEEN(p_to, p_from)/12);
l_from := ADD_MONTHS(p_from, l_years * 12);
l_interval := (p_to - l_from) DAY(3) TO SECOND(0);
return l_years || ' Years '
|| extract (day from l_interval) || ' Days '
|| extract (hour from l_interval) || ' Hours '
|| extract (minute from l_interval) || ' Minutes '
|| extract (second from l_interval) || ' Seconds';
end datediff;
/
SELECT
datediff( TO_DATE('1981-04-01 10:11:13','YYYY-MM-DD HH24:MI:SS'),
TO_DATE('2022-04-03 17:48:09','YYYY-MM-DD HH24:MI:SS')) as diff FROM DUAL;
DIFF
41 Years 2 Days 7 Hours 36 Minutes 56 Seconds
SELECT
datediff (TO_TIMESTAMP('1981-04-01 10:11:13.551000000', 'YYYY-MM-DD HH24:MI:SS.FF'),
TO_TIMESTAMP('2022-04-03 17:48:09.878700000', 'YYYY-MM-DD HH24:MI:SS.FF')) as diff FROM DUAL;
/* want to show fractional difference here */
DIFF
41 Years 2 Days 7 Hours 36 Minutes 56 Seconds

Answer 1

You want to pass TIMESTAMP arguments to the function and when you add years you also need to ensure that you propagate the fractional component of the timestamp (since ADD_MONTHS returns a DATE data-type without fractional seconds):
CREATE OR REPLACE FUNCTION datediff (p_from timestamp, p_to timestamp)
return varchar2 is
l_years PLS_INTEGER;
l_from TIMESTAMP;
l_interval interval day(3) to second(6);
begin
l_years := TRUNC(MONTHS_BETWEEN(p_to, p_from)/12);
l_from := CAST(TRUNC(ADD_MONTHS(p_from, l_years * 12), 'MI') AS TIMESTAMP)
+ NUMTODSINTERVAL( EXTRACT(SECOND FROM p_from), 'SECOND' );
l_interval := (p_to - l_from) DAY(3) TO SECOND(6);
return l_years || ' Years '
|| extract (day from l_interval) || ' Days '
|| extract (hour from l_interval) || ' Hours '
|| extract (minute from l_interval) || ' Minutes '
|| extract (second from l_interval) || ' Seconds';
end datediff;
/
Then:
SELECT datediff(
TIMESTAMP '1981-04-01 10:11:13.551000000',
TIMESTAMP '2022-04-03 17:48:09.878700000'
) as diff
FROM DUAL;
Outputs:
DIFF
41 Years 2 Days 7 Hours 36 Minutes 56.3277 Seconds
fiddle