How many companies have launched their rockets from the Vandenerg Air base?
SELECT DISTINCT COUNT(?uri) WHERE { ?x <http://dbpedia.org/ontology/launchSite> <http://dbpedia.org/resource/Vandenberg_Air_Force_Base> . ?x <http://dbpedia.org/ontology/manufacturer> ?uri  . ?uri <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <http://dbpedia.org/ontology/Company>}
Vandenberg_Air_Force_Base