[Qgis-user] Problem filtering table on columns with NULL values

[Bernd Vogelgesang]

Hi Chris,

I'm a bit confused: I just stated, that I use a filter !='xyz', but not
only these rows are ommited, but also those with NULL values.
I do not try to filter for NULL, I just want the query to NOT filter
them out.

So what I can do to keep the NULLs and just get rid of the xyz?

Cheers,

Bernd

On 15.10.20 16:56, chris hermansen wrote:
> Bernd and list,
>
> On Thu, Oct 15, 2020 at 5:18 AM Bernd Vogelgesang <bernd.vogelgesang at gmx.de>
> wrote:
>
>> Hi,
>>
>> just hit a problem when working with a table from an .ods file.
>>
>> To work with the data, I have to exclude some values from a field, where
>> some entries also have NULL values.
>>
>> When I now filter on the value I do not need ("field" != 'xyz'), also
>> the rows with  NULL values in that field are filtered out, which is not
>> what I want.
>>
> In databases that support NULL values it's customary to use "IS NULL"
> rather than "= NULL".   The rationale is that a boolean expression
> involving NULL values can't be true nor false since the meaning of NULL is
> "unknown".
>
>
>> As I do not want to "invent" data for those rows just to make it work, I
>> wonder if this is a bug or if there is a workaround for this problem.
>>
> I just tried this with the QGIS select calculator (IS NULL) and it seems to
> work fine there.
>
>
>
>