QGIS Expression: count - how to apply filter

Question

I have a table of parcels. Each parcel can have multiple land use types (not necesarily distinct). Those are stored in another table - so in the UseType table, a parcel can show up as wineyard, agriculture, wineyard and orchard.

To get to know how many usetypes I have for each parcel, so my approach was:

count( "usetype",group_by:="parcel_ID")

Unfortunately, several features in the UseType table have NULL in the column "usetype" - how can i exclude them from the count?

Answer 1

This should do it:

count("usetype",group_by:="parcel_ID",filter:="usetype" is not NULL)