apply rtrim on DATE data

Hi All,
The sql below does not return anything,
select DTE_SYSDATE

        from A_T_PR_TAXONOMY
	 WHERE DTE_SYSDATE = to_date( 20071031, 'yyyymmdd')

while these two return some rows
select DTE_SYSDATE

        from A_T_PR_TAXONOMY
	 WHERE rtrim(DTE_SYSDATE) = to_date( 20071031, 'yyyymmdd')

select  DTE_SYSDATE
        from A_T_PR_TAXONOMY
	 WHERE DTE_SYSDATE LIKE to_date( 20071031, 'yyyymmdd')

results:

31-OCT-07
31-OCT-07
31-OCT-07
31-OCT-07

DTE_SYSDATE is a DATE type field in the table A_T_PR_TAXONOMY. I am confused at why the rtrim can make this difference. Received on Thu Nov 01 2007 - 14:50:48 CDT