Hmm... That's an interesting example. It definitely makes sense to enable features like that. However, I'm not sure it's a place where you want to abandon fore

Hmm... That's an interesting example. It definitely makes sense to enable features like that. However, I'm not sure it's a place where you want to abandon foreign-key consistency. To display the song on the playlist (greyed-out, Spotify-style) you need its name and info, and you probably want to keep artist and album links valid as well. It sounds like this is actually a perfect use-case for a soft-delete: keep the song metadata in the songs table and mark it as nonplayable. This keeps the artist page, album page, and any links to the song itself valid, just greyed out when you get there.