[MapServer-users] NULL-EXPRESSION

[Richard Greenwood]

Have you tried making your CLASS for NULLs the last of the three classes
and with no EXPRESSION? The first two classes would pick up 2000 and 2100
and then anything not matching would be in the third class. This works in
most cases but I haven't tried it with NULLs.

Rich

On Fri, Mar 28, 2025 at 4:36 AM Björn Danielsson via MapServer-users <
mapserver-users at lists.osgeo.org> wrote:

> This works for me.
> Try this:
>
> Create two layers with the same name and group.
>
> Layer 1 ( takes care of values 2000 and 2100) :
> LAYER
>     NAME  "A"
>    GROUP "A"
>    .....
>
>    PROCESSING 'NATIVE_FILTER=gst IS NOT NULL'
>
>   CLASS for 2000
> ....
>
>   CLASS for 2100
> ....
>
> END
>
> Layer 2 ( value = NULL ) ❤️
>
> LAYER
>    NAME  "A"
>    GROUP "A"
>    ....
>
>   PROCESSING 'NATIVE_FILTER=gst IS NULL'
>
>  CLASS for NULL
> ....
>
> END
>
>
> ------------------------------
> *Från:* MapServer-users <mapserver-users-bounces at lists.osgeo.org> för
> Seth G via MapServer-users <mapserver-users at lists.osgeo.org>
> *Skickat:* den 28 mars 2025 10:43
> *Till:* angelique.kroisl at stadt-koeln.de <angelique.kroisl at stadt-koeln.de>;
> MapServer Users <mapserver-users at lists.osgeo.org>
> *Ämne:* Re: [MapServer-users] NULL-EXPRESSION
>
> Hi,
>
> Unfortunately, MapServer doesn't have a NULL type.
> The workaround is to create a database view or query that will set the
> NULL to a numeric value of your choosing, e.g. -1 and then use that value
> in the CLASS expressions.
>
> Seth
>
> --
> web:https://geographika.net & https://mapserverstudio.net
> mastodon: @geographika at mastodon.social
>
> On Fri, Mar 28, 2025, at 8:55 AM, Angelique Kroisl via MapServer-users
> wrote:
>
> Hello,
>
> I'm trying to create a class using the class item "gst."
>
> The attribute in the database can only have three values (2000, 2100, and
> <NULL>).
>
> Unfortunately, I can't create the NULL EXPRESSION.
>
>
>
> I've already tried the following:
>
> EXPRESSION IS NULL
>
>
>
> EXPRESSION "<NULL>"
>
>
>
> EXPRESSION <NULL>
>
>
>
> EXPRESSION EMPTY
>
>
>
> What is the correct syntax for this?
>
>
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-- 
Richard W. Greenwood
www.greenwoodmap.com
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