How many {symptoms} are for {mercury poisoning} ?
Give me the number of symptoms for mercury poisoning.
How many symptoms are there of mercury poisoning?
SELECT ( COUNT ( ?q ) AS ?y ) { resource:mercury_poisoning property:symptoms ?q }
SELECT (COUNT(?obj) AS ?objs ) {
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#subject> <http://wikidata.dbpedia.org/resource/Q408089> .
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#predicate> <http://www.wikidata.org/entity/P780> .
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#object> ?obj .
} 

SELECT (COUNT(?obj) AS ?value ) { wd:Q408089 wdt:P780 ?obj }
34