How do I identify which features have NULL attributes in the attribute table of a shapefile?
When i try [field]= 'NULL' it selects the features with value = 0 (see picture)
asked Oct 24, 2011 at 14:55
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6 Answers
Have you tried replacing the "=" with "is"? I don't have QGIS in front of me, but that is pretty common database select syntax for working with NULL values.
pedonal is NULL
answered Oct 24, 2011 at 16:05
I beat my brains about this one. The field name is "ASSETID", it is either a value or NULL. But actually the field was a text field (KML). I tried..
"ASSETID" ISNULL, "ASSETID" IS NULL, ISNULL("ASSETID"), "ASSETID" = "" NOTHING WORKED!
However
"ASSETID" = '', "ASSETID" IN ('') did work also for search "ASSETID" in ('2251', '4321' etc)
Archaic but workable.
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Whilst this works, I think QGIS needs to improve this somehow - The expression documentation specifically states "To test for NULL use an IS NULL or IS NOT NULL expression."– nr_ausOct 7, 2021 at 2:35
Instead of "Null",
Try:
[FieldName] IS None
To select NULL values, click your field. then type in "is NULL." It should look like this: "Field" is NULL. No apostrophe mark (') around the word NULL. Apostrophes are needed around the defined values.
This video instructs you how to update these selected Null values from another shapefile (layer). https://youtu.be/O2hkvJjR2_s
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6This video may answer the question but it can get offline someday. So it would be useful if you could include a short summary in your answer. Aug 23, 2019 at 23:28
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2Link-only answers are often deleted as non-answer Answers, because the information is not present in the Answer itself.– VinceAug 24, 2019 at 23:15
Try:
Pedonal = ''
- that should work!
answered Oct 24, 2011 at 15:26
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that works for text fields...i'm using numerical fields, and that selects values = to 0 Oct 24, 2011 at 15:48
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