Great question. Nulls have a very precise definition in Xcalar.
Nulls are the value Xcalar Design displays for JSON data source containing null as a value.
In other words, nulls only appear:
* In datasets created from JSON data.
* Represent the field value: null or None (not in quotes).
In this circumstance, if you use the Map operation isNull to assess the field, the result will be True.
For more information on FNFs, please refer to this post.
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