For how many different teams have the players debuted in Houston Astros played?
SELECT DISTINCT COUNT(?uri) WHERE { ?x <http://dbpedia.org/ontology/debutTeam> <http://dbpedia.org/resource/Houston_Astros> . ?x <http://dbpedia.org/ontology/team> ?uri  . ?uri <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <http://dbpedia.org/ontology/SportsTeam>}
Houston_Astros