I have this query to get the population of cities and the country they belong to:
SELECT ?city (?population as ?city_pop) ?country ?countryLabel ?continent ?continentLabel ?cityLabel
WHERE {
SERVICE wikibase:label { bd:serviceParam wikibase:language "[AUTO_LANGUAGE],en". }
?city wdt:P31 wd:Q515.
OPTIONAL { ?city wdt:P1082 ?population. }
OPTIONAL { ?city wdt:P17 ?country. }
OPTIONAL { ?city wdt:P30 ?continent. }
}
LIMIT 10
But how can I expand this query to also return the population of the entire country?
I've added this statement to the query
OPTIONAL { ?country wdt:P17 ?population. }
but then I get timeouts.
Bonus: I think getting the continent name for "country" instead of "city" would be more reliable, too.
Actually, my final query will be to return the most-populated city in each country, with the following structure:
city_name, city_population, country_name, country_population, continent_name
Here's a query from the tutorial that gives the max populated city in a country, but similar issues expanding to get the entire country's population in the same row
SELECT ?country (MAX(?population) AS ?maxPopulation)
WHERE
{
?city wdt:P31/wdt:P279* wd:Q515;
wdt:P17 ?country;
wdt:P1082 ?population.
}
GROUP BY ?country
For the record, I've tried the downloads at Geonames but I find some inconsitencies: for example, "city" population of Singapore varies from "country" population of Singapore when there is only one city in Singapore (from two files, perhaps from two sources).
