> NULL = Program haven't read the database yet and doesn't know. NULL1 = Program have read the database and it's null. NULL2 = it was null from where this collector database read this data.
It's not a valid computing problem. In your example there's no difference whatsoever between NULL1 and NULL2, because it doesn't matter where it came from, and as for the difference between NULL and NULL1 - it's irrelevant, because if we know that the field exists, we have the database.
> "decades ago"
I'm fairly sure nobody needed more than 1 type of NULL decades ago, and certainly nobody needs more than 1 type of NULL now.
It's not a valid computing problem. In your example there's no difference whatsoever between NULL1 and NULL2, because it doesn't matter where it came from, and as for the difference between NULL and NULL1 - it's irrelevant, because if we know that the field exists, we have the database.
> "decades ago"
I'm fairly sure nobody needed more than 1 type of NULL decades ago, and certainly nobody needs more than 1 type of NULL now.