I have a point layer (Dormouse) linked to a child geometry-less table (DormouseSurveyData) with a 1-n relationship. I am trying to set up the symbology of the point layer to change color dependent on if there is a value in the 'Presence' field of my child table.
I am aware that I could either join the tables or create a virtual layer to achieve this but I need the symbology to update as the records are updated so that when data is input in the field the symbology will dynamically update accordingly.
I have tried many different variations but the ones i thought most likely to work are below:
case
when dbquery('DormouseSurveyData','Presence','Tube_ID = attribute($currentfeature,'id')')
then color_rgb(0,200,0)
when 'DormouseSurveyData_2acaff7f_d2b5_47a2_875c_0859987007d7.Tube_ID' = 'Dormouse.id' and 'DormouseSurveyData_2acaff7f_d2b5_47a2_875c_0859987007d7.Presence' = "False"
then color_rgb(200,0,0)
else color_rgb(0,0,200)
end
case
when dbvalue('DormouseSurveyData','Presence','Tube_ID', 'ID')
then color_rgb(0,200,0)
when dbvalue('DormouseSurveyData','Presence','Tube_ID', 'ID')
then color_rgb(200,0,0)
else color_rgb(0,0,200)
end
The relationship links Dormouse.id to DormouseSurveyData.Tube_ID
Below are snippets of the two tables. Both with testing data.
When I run either expression in the data override for the fill color of my symbology i just get the 'else' result (ie blue).
Best Answer
Have you tried relation_aggregate function for classification of the layer?
E.g.
relation_aggregate function brings the id or what ever field you need "Up" to your visualization layer and then you can classify your data based on the other 1:N table values.