You can convert dates to characters using the TO_CHAR() function as shown in the following examples:

SELECT TO_CHAR(SYSDATE, 'HH:MI:SS') FROM DUAL;

04:49:49

SELECT TO_CHAR(SYSDATE, 'HH24:MI:SS.FF') FROM DUAL;

-- Error: SYSDATE has no fractional seconds

SELECT TO_CHAR(SYSTIMESTAMP, 'HH24:MI:SS.FF9') FROM DUAL;

16:52:57.847000000

SELECT TO_CHAR(SYSDATE, 'SSSSS') FROM DUAL;

-- Seconds past midnight

69520