GROUP BY - Accessing properties of the grouped set

What I’m trying to do

For this scenario, I have two types of notes in an “Efforts” folder: Areas and Projects. Projects can be nested under areas. This nesting is done by linking to the area note in the “up” property of the project. I’m attempting to create a table of areas, return the “summary” property of the area note, and the count of projects underneath the area. Everything works except getting the summary field. I’m not sure of the appropriate way to pull this information in:

TABLE WITHOUT ID
join(area, ", ") as "", area.frontmatter.summary as "Summary", length(rows.file) as "Active Projects"
FROM "Efforts"
WHERE icontains(tags, "type/project") 
GROUP BY file.frontmatter.up AS area

Things I have tried

I’ve tried area.frontmatter.summary, area.summary, area.file.frontmatter.summary and various other combinations. I’m hoping this is possible without getting into js. Areas and projects can also be identified by their “tags” property containing either “type/area” or “type/project” if that matters.