How many {interested in} are to/by {philosophy} ?
What is the approximate number of individuals that are interested in philosophy?
How many individuals are interested in philosophy?
SELECT ( COUNT ( ?n ) AS ?r ) { ?n property:interested_in resource:philosophy }
SELECT (COUNT(?sub) AS ?subs ) {
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#subject> ?sub .
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#predicate> <http://www.wikidata.org/entity/P2650> .
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#object> http://wikidata.dbpedia.org/resource/Q5891 .
} 

SELECT (COUNT(?sub) AS ?value ) { ?sub wdt:P2650 wd:Q5891 }
17