Null Fields

Null (that is, not present) fields are handled in a special way by &NDBSCAN:

A null field never matches a field to value test. A record with field SURNAME not present is not equal to a supplied value, nor is it not equal to a supplied value. This 'null result' carries through the scan action table.
A null field can only be selected using the ABSENT or IS NULL operators.

This handling of null fields by &NDBSCAN is consistent with other &NDB verbs. Thus, disjoint record types work as expected.