Calculate the ratio

This is probably quite simple. I want to calculate the ratio of each country (gwcode) which experiences a 1 in one column (cf).

Structure:

gid; gridyear; gwcode; area; cf

I want to select the SUM(area) WHERE cf = 1 into one column, and SUM(area) WHERE cf = 0 into another column and group by gridyear and gwcode.

Then i can see the ratio of the area of each country affected by cf.

Any suggestions?

Thanks.

A.