How many {external subproperty} are for {seat} ?
a seat needs what subpropertyies?
how much external subpropertyies are needed for a seat?
SELECT ( COUNT ( ?k ) AS ?t ) { resource:seat property:external_subproperty ?k }
SELECT (COUNT(?obj) AS ?objs ) {
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#subject> <http://wikidata.dbpedia.org/resource/Q2731419> .
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#predicate> <http://www.wikidata.org/entity/P2236> .
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#object> ?obj .
} 

SELECT (COUNT(?obj) AS ?value ) { wd:Q2731419 wdt:P2236 ?obj }
0