[Qgis-user] Select by Expression: exclusive (not inclusive)

[Andy Harfoot]

Out of curiosity, what happens if you execute the same query via the 
Virtual layer dialog or through the DB Manager? This would highlight any 
differences between QGIS Expression SQL and a DBMS (the SQLite engine).

On 15/07/2021 08:17, Andrew Hughes wrote:
> *CAUTION:* This e-mail originated outside the University of Southampton.
> Thanks Marco,
>
> You've answered my question, so thank you. For reference, I've never 
> see this in any sql rmdbs.
>
> Some examples my help the community, hopefully I will be able to 
> contribute sooner or later.
>
> Thanks again!
> Andrew
>
>
> On Wed, 7 Jul 2021 at 17:43, GMAIL <casalbonim at gmail.com 
> <mailto:casalbonim at gmail.com>> wrote:
>
>     This is how sql works.
>     You want to apply a function to one column, and the column you are
>     comparing must have a value.
>     Consider this: tag_service != 'xxx' or null != 'xxx'. Null can't be
>     equal or unequal to any value. Even null = null or null != null
>     returns
>     false
>
>     hth
>     marco
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-- 
Andy Harfoot

Skype: gdi_ajph
Teams: ajph at soton.ac.uk

GeoData Institute
University of Southampton
Southampton
SO17 1BJ

www.geodata.soton.ac.uk

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