I am tracking renewable projects in my country. I have a "Developments" layer, which shows polygons on a map representing projects. I also have a "Stakeholders" table (no geometry) that lists project developer companies. Therefore, I can track that "Project A" was developed by "Company X" and "Company Y".
The layers are related in a many-to-many relationship as follows:
where the names in red represent the names of the relations in QGIS' project properties.
I have over 700 developments in my project. I have linked developers to most of them, but some don't have a developer yet as I am still investigating.
I need to find the right advanced filter (expression) that will help me filter my attribute table to show only the developments that don't have a developer yet.
I have tried with the relation_aggregate() function as follows:
relation_aggregate( relation:= 'Developers', aggregate:= 'array_agg', expression:= "stakeholder_id" ) and manage to get an array with the "fid" of the developers of each development, i.e. [12, 17, 104].
However, I am stuck at the next step: how do I filter out only those cases with a returned array that's empty? i.e. those that are []
I have tried:
relation_aggregate( relation:= 'Developers', aggregate:= 'array_agg', expression:= "stakeholder_id" ) IS NULL but it does not work.
