What are the names of all the playlist?
select name from playlists;
For each, what are the names of their tracks?
select t3.name, t2.name from playlist_tracks as t1 join playlists as t2 on t2.id = t1.playlist_id join tracks as t3 on t1.track_id = t3.id;
For each playlist name, count the number of tracks!
select t2.name, count(t1.track_id) from playlist_tracks as t1 join playlists as t2 on t2.id = t1.playlist_id group by t1.playlist_id;
Show the only the names of the playlists with more than 100!
select t2.name from playlist_tracks as t1 join playlists as t2 on t2.id = t1.playlist_id group by t1.playlist_id having count(t1.track_id) > 100;