oracle difference between two dates in seconds

1SELECT (END_DT - START_DT) * 60 * 60 * 24 FROM MY_TABLE;   	-- Seconds
2SELECT (END_DT - START_DT) * 60 * 24 FROM MY_TABLE;   		-- Minutes
3SELECT (END_DT - START_DT) * 24 FROM MY_TABLE;   			-- Hours

1select floor(months_between(date '2012-10-10', date '2011-10-10') /12) from dual;
2
3select floor(months_between(date '2012-10-9' , date '2011-10-10') /12) from dual;
4

1  v_numvar := dt1-dt2;