DBPedia Sparql端点：关键字可选

Question

I'm trying to run the following SPARQL query:

SELECT ?band, ?genre
WHERE
{
      ?band a umbel-rc:Band_MusicGroup.
      OPTIONAL{?band dbo:genre ?genre}.
}

but in the result there are no bands for which a dbo:genre is not defined (such as Coldplay look here ). Optional does not work in DBpedia?

Answer 1

Thank's to @StanislavKralin I understand now that you might be confused by missing data in the resultset, eg Coldplay. The short answer here is that the Virtuoso triple store on which DBpedia is deployed has a default resultset size limit of 10000 , ie at most 10000 rows will be returned with a single query. If you want to get more results you have to use something that's often referred to as pagination, ie for each chunk you append

ORDER BY ?band LIMIT 10000 OFFSET 10000*chunk