Extract Function

We can get YEAR | MONTH | DAY | HOUR | MINUTE | SECOND values using To_char Function also. Where do we use this extract function? Could anyone please me give an example of the situation where can't use T0_char function and get result only by using extract function?

The extract function extracts a value from a date or interval value
example
SELECT
EXTRACT(year FROM systimestamp) ,EXTRACT(month FROM systimestamp),
EXTRACT(day FROM systimestamp) ,EXTRACT(hour FROM systimestamp),
EXTRACT(minute FROM systimestamp),EXTRACT(second FROM systimestamp),
EXTRACT(timezone_hour FROM systimestamp) ,EXTRACT(timezone_minute FROM systimestamp) ,EXTRACT(timezone_region FROM systimestamp) ,
EXTRACT(timezone_abbr FROM systimestamp)
FROM dual;

For ur second question pls follow this [URL="http://blogs.ittoolbox.com/oracle/jochenvdv/archives/to_char-versus-extract-15959"]link[/URL]