How many {creator} are for {quantum mechanics} ?
Which is the number of creators that are there for quantum mechanics?
How many creators are there for quantum mechanics?
SELECT ( COUNT ( ?y ) AS ?m ) { resource:quantum_mechanics property:creator ?y }
SELECT (COUNT(?obj) AS ?objs ) {
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#subject> <http://wikidata.dbpedia.org/resource/Q944> .
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#predicate> <http://www.wikidata.org/entity/P170> .
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#object> ?obj .
} 

SELECT (COUNT(?obj) AS ?value ) { wd:Q944 wdt:P170 ?obj }
10