[Qgis-user] Filtering NULL values from WFS

[pathmapper]

Michael, can you provide the WFS URL?

On 27.08.2025 07:31, Reetz, Michael (NLPVW) via QGIS-User wrote:
> Dear Chris and Björn,
> 
> yes, I have tried end_date is null first. No records are found with
> this although most record have NULL as end_date.
> 
> Cheers,
> 
> Michael
> 
> VON: chris hermansen <clhermansen at gmail.com>
>  GESENDET: Dienstag, 26. August 2025 17:45
>  AN: Reetz, Michael (NLPVW) <Michael.Reetz at nlpvw.niedersachsen.de>
>  CC: qgis-user <qgis-user at lists.osgeo.org>
>  BETREFF: Re: [Qgis-user] Filtering NULL values from WFS
> 
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> Michael and list
> 
> On Tue, Aug 26, 2025, 07:54 Reetz, Michael (NLPVW) via QGIS-User
> <qgis-user at lists.osgeo.org> wrote:
> 
>> Hello group,
>> 
>> I’ve added a WFS-layer to a project try to define filters on
>> different attributes. It seems not to be possible to filter for NULL
>> values.
>> 
>> Example:
>> 
>> * 1932 records in total
>> * 376 records with a value in a date attribute
>> * 20 records with 2005-12-31 as value
>> 
>> If I set the filter to "end_date" = '2005-12-31' the result is 20
>> records.
>> 
>> If I set the filter to "end_date" != '2005-12-31' the result is 356
>> records. So only records that have an end date are recognized.
>> Record with NULL as end date are ignored.
>> 
>> Filtering in the attribute table with “is_empty_or_null” works
>> but only for selection.
>> 
>> Is this “normal” behaviour with WFS layers or is there a way to
>> define a filter string that work for all records?
> 
> Have you tried
> 
> end_date IS NULL
> 
> Generally speaking (I'm not sure about this specific case) null is
> neither equal nor unequal hence the need for a different logical
> operator, IS.
> 
> Can you combine conditions for example
> 
> end_date IS NULL or end_date = '2005-12-31'
> 
> 
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