query: # https://www.wikidata.org/wiki/Help:Property_constraints_portal
  # popular contraints
  SELECT ?constraint ?constraintLabel ?ct
  WHERE
  {
    {
    SELECT ?constraint (count(*) as ?ct)
    WHERE
    {
      ?item wdt:P2302 ?constraint
    }
    GROUP BY ?constraint
    }
    SERVICE wikibase:label { bd:serviceParam wikibase:language "[AUTO_LANGUAGE],en". }
  }
  ORDER BY DESC(?ct) ASC(?constraint)