Question: Name the sea with Helsinki as one of the shore city and is also an outflow for Danish straits?
SPARQL:
SELECT DISTINCT ?uri WHERE {?uri <http://dbpedia.org/property/cities> <http://dbpedia.org/resource/Helsinki> . ?uri <http://dbpedia.org/property/outflow> <http://dbpedia.org/resource/Danish_straits>  . ?uri <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <http://dbpedia.org/ontology/Sea>}