SELECT DISTINCT ?uri WHERE { ?x <http://dbpedia.org/property/league> <http://dbpedia.org/resource/Ekstraliga_(speedway)> . ?x <http://dbpedia.org/property/nickname> ?uri . }
what are the nicknames of the people who are in Ekstraliga?
SELECT DISTINCT ?b WHERE { ?w property:nickname ?b . . ?w property:league resource:Ekstraliga_(speedway) }
Byki, Lions, Swallows, Sparta
The nicknames of the people whose league is Ekstraliga are [Byki, Lions, Swallows, Sparta].
The  nicknames of the people who are in Ekstraliga Bulls [Byki, Lions, Swallows, Sparta].