query: SELECT ?instance ?championship ?championshipLabel ?start (SAMPLE(?participants) AS ?participants) (COUNT(?participant) AS ?listedParticipants) WHERE {
    ?championship wdt:P31 ?instance . VALUES ?instance {wd:Q19317 wd:Q260858} .
    ?championship wdt:P580 ?start .
    OPTIONAL{?championship wdt:P1132 ?participants}
    OPTIONAL{?championship wdt:P710 ?participant}
    SERVICE wikibase:label{bd:serviceParam wikibase:language "en"}
  }
  GROUP BY ?instance ?championship ?championshipLabel ?start
  HAVING (?participants != ?listedParticipants)
  ORDER BY DESC(?instance) ?start