-- Determine for each country the province in which the total number of purchases of product 0 is the highest; list the name of the country, the name of the province, and the number of purchases, both absolute and as a proportion of the total number of purchases in that country.

-- Expected Heading: RELATION {country CHARACTER, province CHARACTER, abs INTEGER, prop FLOAT}
-- How do you treat the default case as showed in the instructions?
-- How do you treat the case where several provinces of a same country have the same total number of purchases of product 0? You should show all such provinces.


SELECT name AS country, province, abs, prop 
FROM (
	SELECT name AS province, country, max(cnt) as abs, max(cnt)*1.0/sum(cnt) AS prop
	FROM(
		SELECT province, sum(qty) as cnt
		FROM Purchases
		WHERE product = 0
		GROUP BY province
	)
	JOIN Province ON province = Province.ROWID
	GROUP BY country
)
JOIN Country ON country = code
;

-- V2
SELECT country.name, TMP.province, cnt AS abs, cnt*1.0/scnt AS prop
FROM
(
	SELECT province.country AS code, province.name AS province, COUNT(Purchases.qty) AS cnt
	FROM province
	LEFT JOIN Purchases ON Purchases.product = 0 AND Purchases.province = province.ROWID
	GROUP BY province.name
) AS TMP
JOIN (
	SELECT code, province, MAX(cnt) AS mcnt, SUM(cnt) AS scnt FROM (
		SELECT province.country AS code, province.name AS province, COUNT(Purchases.qty) AS cnt
		FROM province
		LEFT JOIN Purchases ON Purchases.product = 0 AND Purchases.province = province.ROWID
		GROUP BY province.name
	)
	GROUP BY code
) AS F ON TMP.code = F.code AND TMP.cnt = F.mcnt
JOIN country ON country.code = TMP.code
;