how to find the diffrence berween two dates

How to find the difference between two dates in informatica.if by usinf date_diff funation,then i am getting systax error while using it.can anybody help me to resolve this prob?

Following is my requirement:-
If the difference between (DW_ONLINE_ATTRS_UPDATE_DTTM and SYSDATE) OR the difference between (DW_GENERAL_ATTR_UPDATE_DTTM and SYSDATE) then retuen 'A' else 'B'.

please tell me the how tyo put query in expression transformation.

The resultant of a DATE_DIFF function is a number. It could be in terms on days, months etc.. In your expression use the resultant value and based on the resultant value +ve or -ve, then return A or B

Raviayyappan is right. Adding to that please make sure the date format must be equal, since SYSDATE may take Time stamp that means date with time that makes the diff. ..........thx