Obtaining ActiveRecords if NOT nil

Question

I would like to be able to gather all records in a table where the user_id is not null. This is what I have but it doesn't seem to be working (even though I've had it working in a seperate project):

named_scope :all_registered, :conditions => ["user_id != ?", nil]

Answer 1

SQL has a specific operator to check for NULL: IS NULL and IS NOT NULL

named_scope :all_registered, :conditions => ["user_id IS NOT NULL"]