How many {field of this occupation} are to/by {retail} ?
What is the number of field occupants for retail?
How many field occupants are there for the {retail} ?
SELECT ( COUNT ( ?o ) AS ?q ) { ?o property:field_of_this_occupation resource:retail }
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/P425> .
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#object> http://wikidata.dbpedia.org/resource/Q126793 .
} 

SELECT (COUNT(?sub) AS ?value ) { ?sub wdt:P425 wd:Q126793 }
2