Regarding
@LyonMNGIS wrote:
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I would expect any null records to show up on the map because they are not equal to hidden. Am I missing something?
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The existence or possibility of NULL means SQL operators implement three-valued or ternary logic. Instead of the true/false outcomes of boolean logic, there are true/false/unknown outcomes. If you write:
check <> 'Hidden'
The records that are NULL return unknown, not true or false. Since the result is unknown, the database will not return them because it is possible they could be 'Hidden', and it only returns records that are guaranteed not to be 'Hidden'.
There are people who strongly oppose allowing or using NULL in any data model, including CJ Date who is credited with creating the relational model that SQL databases partially implement.
I will note that prior to ArcGIS Pro 3.3, Esri's implementation of three-valued logic with certain operators in the file geodatabase was inconsistent with SQL standards and the rest of the industry. Esri fixed the issue to be consistent with everyone else at Pro 3.3, but it also means certain queries can produce different results between Pro 3.2 and earlier and Pro 3.3 and later.
