I am getting duplicate rows on a specific SPARQL query with query.wikidata.org. The duplicates seem to arise when a value has been edited in the references. Besides a BlazeGraph issue this could be my misunderstanding of SPARQL.
For a query that has the issue see: https://www.mediawiki.org/wiki/Talk:Wikidata_query_service and the below:
prefix pr: <http://www.wikidata.org/prop/reference/>
PREFIX wd: <http://www.wikidata.org/entity/>
PREFIX wdt: <http://www.wikidata.org/prop/direct/>
PREFIX wikibase: <http://wikiba.se/ontology#>
PREFIX p: <http://www.wikidata.org/prop/>
PREFIX v: <http://www.wikidata.org/prop/statement/>
PREFIX q: <http://www.wikidata.org/prop/qualifier/>
PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#>
PREFIX prov: <http://www.w3.org/ns/prov#>
SELECT ?work ?workLabel ?author ?authorLabel ?genre ?location ?locationLabel ?geo ?location_statement ?citat WHERE {
?work wdt:P31/wdt:P279* wd:Q386724 .
?work wdt:P50 ?author .
?work p:P840 ?location_statement .
?location_statement v:P840 ?location .
?location wdt:P17 wd:Q35 .
?location wdt:P625 ?geo .
OPTIONAL {
?location_statement prov:wasDerivedFrom ?ref .
?ref pr:P1683 ?citat .
}
SERVICE wikibase:label { bd:serviceParam wikibase:language "da,en" . }
}