Oracle sysdate format change from dd/mm/yy to ddmmyy - sql

Question

The data length in our production DB, DATE data type, is 7, the sysdate function return 8 characters (dd/mm/yy) .
Is there any way to eliminate '/' and only populate 'ddmmyy'.
Tried the below but no luck.
INSERT INTO TESTER(tablename,columnname,defaultdate,prime_number) VALUES ('tabL7845','field894',REPLACE(SYSDATE,'/',''),105);
INSERT INTO TESTER(tablename,columnname,defaultdate,prime_number) VALUES ('ta68888','fiG987',TO_CHAR(sysdate,'MMDDYY'),180);
INSERT INTO TESTER(tablename,columnname,defaultdate,prime_number) VALUES ('tab345','field464',TRIM(BOTH '/' FROM SYSDATE),65);
Row is getting inserted but in table i could find the same sysdate format,
for eg ) 07/08/20
How can i populate as 070820
Trigger code :
SET SERVEROUTPUT ON;
CREATE OR REPLACE TRIGGER def_trig
BEFORE INSERT OR UPDATE OF datedef ON Test
REFERENCING OLD AS O NEW AS N
FOR EACH ROW
DECLARE
V_DATA_LENGTH NUMBER;
V_DATA_TYPE VARCHAR2(15);
BEGIN
SELECT DATA_LENGTH,DATA_TYPE
INTO V_DATA_LENGTH,V_DATA_TYPE
FROM all_tab_columns
WHERE table_name = :n.tablename
AND column_name =:n.columnname
IF INSERTING THEN
IF v_data_type = 'DATE' THEN
IF length(:n.datedef) > V_DATA_LENGTH THEN
RAISE_APPLICATION_ERROR(-20001,'DATE FIELD LENGTH IS MORE THAN THE CORESPONDING COLUMN DATA LENGTH');
END IF;
ELSE
DBMS_OUTPUT.PUT_LINE('INSERT IS SUCCESSFUL');
END IF;
END if;
END;
/

Answer 1

Dates in Oracle do not have any internal sort of text formatting; they are stored as binary. If you want to view a SYSDATE value in a certain text format, then use TO_CHAR with the appropriate format mask:
INSERT INTO TESTER (tablename, columnname, defaultdate, prime_number)
VALUES ('ta68888', 'fiG987', sysdate, 180); -- just insert plain SYSDATE here
SELECT
tablename,
columnname,
TO_CHAR(defaultdate, 'DDMMYY'), -- then view SYSDATE however you want
prime_number
FROM TESTER;
Here is the output from the above query:
Demo

Answer 2

Internally dates are stored as a structure of 7 1byte integers, that's where the length 7 comes from. From that structure any valid format can be displayed without any data change. To see this select the same column with multiple formats. For example:
alter session st nls_date_format = 'hh24:mi:ss dd-Mon-yyyy';
select defaultdate
from teaster
where defaultdate is not null
and row_num<2;
alter session set nls_date_format = 'Dy dd-Mon-yyyy # hh24:mi:ss' ;
select defaultdate
from teaster
where defaultdate is not null
and row_num<2;
To get a glimpse at the internal format run:
select defaultdate, dump(defaultdate) from teaster;
This will show you the default date (interpreted as directed by nls_date_format) and a glimpse of the internal structure.