This is my first question on this site: it is probably already been exposed many times, but try to forgive me if I could not find it. Secondly, English is not my native language, I will try to be as clear as possible.
I am creating an archaeological map with a simple point shapefile. But I need to be able to enter multiple values in a single field of the attribute table. For example, an archaeological site can belong to different phases, in my case "Achaemenid" and "Sasanian". How do I do this thing, making sure that QGIS consider "Achaemenid" and "Sasanian" two different attributes even if they are in the same field?