In my mysql database I stored empty strings as NULL's, so that I can test 
fields to be nil. 

(It's shorter, nicer and more logical to test "if field" rather than
"if field == ''")

But when I edit a record, all NULL's in char fields are replaced with an 
empty string (''). 

Is there a way to prevent this? 
Or is my idea wrong in the first place?

-- 
Wybo