Topic: attribute.length in named_scope query.. syntax

I have this as a named scope in my Account model

named_scope :with_country_code, lambda { { :conditions => ['country IS NOT NULL'] } }

which is working..

but its also returning records where the 'country' is "" (nothing, but not NULL)

so i was wanting to add in something like :conditions => ['country IS NOT NULL AND country.length =? 2']

But that syntax is wrong..  Could someone please point me in the right direction on getting the length of the attribute in the query? thanks!