User:TweetsFactsAndQueries/Queries/number of living people who have walked on the moon

Originally posted on Twitter and on Mastodon. Based on number of living former heads of government over time.

#defaultView:LineChart
SELECT ?date (COUNT(DISTINCT ?item) AS ?count)
WITH {
  # get all the dates where the number of living people who have walked on the moon changed
  # (person walked on the moon or person died)
  SELECT DISTINCT ?date WHERE {
    {
      # person walked on the moon
      ?item p:P793 [
        ps:P793 wd:Q42882411;
        pq:P580 ?date_
      ].
    } UNION {
      # person died
      ?item p:P793/ps:P793 wd:Q42882411;
            wdt:P570 ?date_.
    }
    # for each date, inject a second date, one day before,
    # so that we get a straight line until that date and then a steep climb/drop for the real change,
    # instead of a diagonal slope over the entire preceding period
    VALUES ?toggle { true false }
    BIND(IF(?toggle, ?date_, ?date_ - "P1D"^^xsd:duration) AS ?date)
  }
} AS %dates
WHERE {
  # inject the current time as another date, so that the chart continues until the present day
  { INCLUDE %dates. } UNION { BIND(NOW() AS ?date) }
  # main query: find all living people who have walked on the moon at each date
  ?item p:P793 [
    ps:P793 wd:Q42882411;
    pq:P580 ?walkdate
  ].
  FILTER(?date >= ?walkdate) # must have walked on the moon already
  OPTIONAL { ?item wdt:P570 ?died. }
  FILTER(!BOUND(?died) || ?date < ?died) # must not yet have died
}
GROUP BY ?date
ORDER BY ?date

Try it!