ORACLE Procedure with TIMESTAMP - oracle

Question

I try to write a procedure to know the datetime from a timezone to another timezone
I can't compile because the format date is not valid and I don't know how to manage the variable.
Can you give me a tip, please
create or replace PROCEDURE DATETIME_FROM_TO
(
VALUE$DATETIME in date,
VALUE$FROM in varchar2,
VALUE$TO in varchar2,
FLAG in number
) AS c1 SYS_REFCURSOR;
begin
VALUE_DATETIME := VALUE$DATETIME;
VALUE_FROM := VALUE$FROM;
VALUE_TO := VALUE$TO;
if FLAG=12 then
open c1 for
select to_char(from_tz(TIMESTAMP 'VALUE_DATETIME', 'VALUE$FROM') at time zone 'VALUE$TO','DD/MM/YYYY HH:MI PM') as localtime into c1 from dual;
else
open c1 for
select to_char(from_tz(TIMESTAMP 'VALUE$DATETIME', 'VALUE$FROM') at time zone 'VALUE$TO','DD/MM/YYYY HH24:MI') as localtime into c1 from dual;
end if;
DBMS_SQL.RETURN_RESULT(c1);
close c1;
end;
thank you

Answer 1

I'm not sure why you want to go down the hugely complicated route of using a cursor and returning a string in a result set.
Just write a simple function that takes a TIMESTAMP argument (if you pass it a DATE it will be implicitly cast to a TIMESTAMP) and if you want to format it as a string then you can call TO_CHAR on the return value as required.
CREATE FUNCTION change_timezone(
i_datetime TIMESTAMP,
i_from_tz VARCHAR2,
i_to_tz VARCHAR2
) RETURN TIMESTAMP WITH TIME ZONE DETERMINISTIC
IS
BEGIN
RETURN FROM_TZ( i_datetime, i_from_tz ) AT TIME ZONE i_to_tz;
END;
/
Then you can call it using:
SELECT change_timezone( DATE '1970-01-01', 'UTC', 'Europe/Berlin' )
FROM DUAL;
Which outputs (depending on your NLS_TIMESTAMP_TZ_FORMAT setting):
| EPOCH_TIME_IN_GERMANY |
| :-------------------------------- |
| 1970-01-01 01:00:00.000000000 CET |
and if you want it with a particular format then:
SELECT TO_CHAR(
change_timezone( DATE '1970-01-01', 'UTC', 'Europe/Berlin' ),
'DD/MM/YYYY HH12:MI PM'
) AS formatted_epoch_time_in_germany
FROM DUAL;
Which outputs:
| FORMATTED_EPOCH_TIME_IN_GERMANY |
| :------------------------------ |
| 01/01/1970 01:00 AM |
If you really want to incorporate the string conversion (don't, do the conversion outside the function) then you could use:
CREATE FUNCTION format_as_timezone(
i_datetime TIMESTAMP,
i_from_tz VARCHAR2,
i_to_tz VARCHAR2,
i_use_24hr NUMBER DEFAULT 1
) RETURN VARCHAR2 DETERMINISTIC
IS
BEGIN
RETURN TO_CHAR(
FROM_TZ( i_datetime, i_from_tz ) AT TIME ZONE i_to_tz,
CASE i_use_24hr
WHEN 1
THEN 'DD/MM/YYYY HH24:MI'
ELSE 'DD/MM/YYYY HH12:MI AM'
END
);
END;
/
db<>fiddle here