Question: Which countries adopted the Euro?
SPARQL:
PREFIX dbp: <http://dbpedia.org/property/>
PREFIX dbo: <http://dbpedia.org/ontology/>
PREFIX res: <http://dbpedia.org/resource/>
PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>
SELECT DISTINCT ?uri
WHERE {
          ?uri rdf:type dbo:Country .
        { ?uri dbo:currency res:Euro . } 
        UNION 
        { ?uri dbp:currencyCode 'EUR'@en . }
}