I have a layer with polygons (let's call it "woods") that is intersected by "n" line-objects ("roads"). Every road has an unique attribute roadid.
I need to add ALL the roadid's (not only the first QGis finds) to the woods-polygons-layer they intersect for latter use. Preferably all the roadid's should be in one new attribute column of the "woods", divided by e.g. ",".
If there was only one road in every wood i could use the "join attribute by position" tool to get roadid's on the polygons. The wanted attribute is an unique string so it doesn't help to sum/average/min/max the fields, and there is no option to bind them together as strings divided by ",".
Edit: There is no solution without the help of plugins or external programms by now (see comment by Matthias Kuhn below).
(QGIS 2.10.1-Pisa)