query: # Which White House chief of staff had the shortest tenure?
  # 
  SELECT ?item ?itemLabel ?start ?end ?days
  WHERE 
  {
    ?item wdt:P31 wd:Q5 .            # Human
    ?item wdt:P39 wd:Q786242 .       # position held: White House chief of staff
    ?item p:P39 ?positionstatement . # grab statement
    ?positionstatement ps:P39 ?position ;  # grab position
                       pq:P580 ?start .    # grab start date
    ?position wdt:P279* wd:Q786242 .       # re-filter for White House chief of staff
    OPTIONAL { ?positionstatement pq:P582 ?end } # grab optional end date
    bind(floor(?end - ?start) as ?days)    # calculate number of days served
    SERVICE wikibase:label { bd:serviceParam wikibase:language "[AUTO_LANGUAGE],en". }
  } ORDER BY ?days