Question: For how many teams have the league players of Czech Extraliga, previously played?
SPARQL query:
PREFIX prop: <http://dbpedia.org/property/>
PREFIX onto: <http://dbpedia.org/ontology/>
SELECT DISTINCT COUNT(?uri) WHERE { ?x prop:league <http://dbpedia.org/resource/Czech_Extraliga> . ?x onto:formerTeam ?uri  . }