Is it possible to substract the entire date parameters(year,month,date) by using a single or two functions .

yes, it is

if you would give a more realistic example, i can give a more realistic answer

Suppose i have two date columns say 'DATE1' and 'DATE2' which has values "2008-09-15" and "2007-07-11" .

now i want the diff of these two columns in date format, i mean the diff should return a date value.

oh really? and what is the "date value" that you would like to see from this particular calculation?

Find the difference in days, and then add this on to the base date (equivalent to 0)?

The manual should be your friend