QGIS filtering a whole field using NOT

Question

I'd like to negate some values from my map using the NOT operator.

However, i need to deselect a whole field which contains over 600 entries so I don't want to select each. Is there a way to do this?

Is it possible to use: NOT SPA_NAME, without specifying the values

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Added from answer:

I have a merged layer with many different soil and land use properties. And I'm trying to select areas that meet certain soil and land use conditions.

So far my expression is: SOIL_TEXTURE = 'clay' OR SOIL_TEXTURE = 'loam' AND LAND_USE = 'arable' AND LAND_USE = 'grassland'

So now I'd like to make sure special protected areas (SPA_NAME field) are excluded from the selection, but there are so many values that is wouldn't make sense to individually select each.

On closer look I am seeing that the command SPA_NAME IS NULL didn't work. Areas that are under special protection are still being selected

Answer 1

You simply can expand your current expression by AND "SPA_NAME" IS NULL.

SOIL_TEXTURE = 'clay' OR SOIL_TEXTURE = 'loam' AND LAND_USE = 'arable' AND LAND_USE = 'grassland' AND "SPA_NAME" IS NULL

Now it should return all clay and loam areas which are grassy or arable and not within a SPA-area.