I have a table with county polygon boundaries (named
"counties"). I need to build a query that identifies a particular county as well as any adjoining counties that share the same border. Have tried breaking this down but I'm missing something. Any ideas?
You can create a Virtual Layer that will query the polygon layer twice and apply the desired filtering.
go to the menu
Layer > Add Layer > Add/Edit Virtual Layer... and enter the query
SELECT b.* FROM myLayer a JOIN myLayer b ON ST_INTERSECTS(a.geometry,b.geometry) WHERE a.id <> b.id AND a.id = 1234