How to label parcels with multiple parcel owners in QGIS?

Question

I have GeoPackage file with parcels (polygons) and an Excel table with parcel owners. As one parcel can have multiple parcel owners I established a one to many relationship. Now I wish to label the parcels with one or more owners (as many as the parcel has).

The parcel layer and Excel table have mutual Parcel IDs.

How could I do this in QGIS?

Answer 1

You can use a custom function in the label expression editor

• Assuming your parcels attribute table is structured like this:

from qgis.core import *
from qgis.gui import *

@qgsfunction(args='auto', group='Custom', referenced_columns=[])
def concat_field_values(feature, parent, context):
    ## get field names of layer using 'context' argument
    fields = context.fields().names()
    
    ## get fields with 'name' in the field name
    fields = [x for x in fields if 'name' in x.lower()]
    
    ## loop through fields and get list of values, excluding null values
    owners = [str(feature.attribute(x)) for x in fields if str(feature.attribute(x)) != "NULL"]
    
    ## join list into string, using the new line escape character
    label_string = '\n'.join(owners)
    
    return label_string

If you are unsure how to make a custom function

• Click the expression editor button

• Select the Function Editor tab
• Make a new function and paste the code
• Click Save and Load Functions

• Back in the Expression tab, enter the function name, followed by parentheses