How many {musical conductor} are to/by {Claudio Abbado} ?
Which is the number of pieces that Claudio Abbado has conducted?
How many pieces has Claudio Abbado conducted?
SELECT ( COUNT ( ?m ) AS ?w ) { ?m property:musical_conductor resource:Claudio_Abbado }
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/P3300> .
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#object> http://wikidata.dbpedia.org/resource/Q151608 .
} 

SELECT (COUNT(?sub) AS ?value ) { ?sub wdt:P3300 wd:Q151608 }
3