How To Get The Status?

I have a table with columns c1, c2, c3, c4.

if all nulls or blanks. Status = 0
if c1 assigned but no c2, c3, and c4, then status = 1
if c2 assigned but no c3 and c4, then status = 2
if c3 .. then ..
if c4 .. then ..

I want to have one SQL to get the status like (ignored checking for
blanks here for demo)

SELECT Status = (if not c4 is null then 4
else not c3 is null then 3
else not c2 is null then 2
else not c1 is null then 1
else 0)
FROM mytable.

Thought of using CASE ... WHEN ... but it is only on one colum.

Any better idea.

Thanks

John