How many {public holiday} are to/by {Boxing Day} ?
Which is the number of the public holidays that are on Boxing Day?
How many public holidays are on Boxing Day?
SELECT ( COUNT ( ?h ) AS ?r ) { ?h property:public_holiday resource:Boxing_Day }
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/P832> .
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#object> http://wikidata.dbpedia.org/resource/Q956699 .
} 

SELECT (COUNT(?sub) AS ?value ) { ?sub wdt:P832 wd:Q956699 }
10