select sysdate from dual
select to_char(sysdate,'yyyy-MM-dd HH24:mi:ss') from dual;
select to_char(sysdate,'yyyy-MM-dd HH24:mm:ss') from dual;
select to_char(sysdate,'yy-mm-dd hh24:mi:ss') from dual
select TO_CHAR(SYSDATE,'YY/MM/DD HH24:MI:SS')
from dual;
select user from dual