Re: Eliminating Nulls

NULLs are not automatically bad. The real questions are:

1. Does this attribute belong with this entity? if yes, then do not split it out.
2. Does this attribute have one or more unknown reasons for a missing value? If yes, then encode them. Example: in ICD (International Classification of Disease) 000.000 means 'undiagnosed' while 999.999' means 'diagnosed, but unknown disease' -- two very different kidns of missing values
3. Does it make sense to drop NULLs form aggregations for this attribute?
4. Is there a natural default value? For numerics this is often zero. For strings, like your example, it is often a note like '{{ to be determined }}' -- I like curvy brackets to force them to sort to the end of a listing and be easy to search.