I tried below query but its not working
select
TO_TIMESTAMP(ColumnName(Data type Date), 'DD-MON-YYYYHH24:MI:SS.FF')
from TableName
where Changedate>='01-Dec-2015'
*I need the result without AM/PM indication. Result will be 15-DEC-2015 15:16:42.045016
If I got your question right you need the output in the mentioned Format. That would be a conversion to character
select to_char(cast(sysdate as timestamp),'DD-MON-YYYY HH24:MI:SS.FF') from dual
Of course in the above the FF would also always be 000000
But if you have a timestamp variable you would not cast
select to_char(systimestamp,'DD-MON-YYYY HH24:MI:SS.FF') from dual