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我想通了。 SELECT DISTINCT ON(country.name)country.name AS country ... working如何在查詢中選擇每個國家/地區的一行
我正在查詢以獲取每個國家/地區的單個最大城市(以人口計)。問題在於,某個國家的一些城市被綁定在相同的人口中,因此查詢返回的國家/地區不止一個城市。 (我試過SELECT DISTINCT country.name,但它給了我相同的輸出)
任何想法?
這裏是我的代碼:
$query = "SELECT country.name AS country, largest_city, sq.pop AS population
FROM lab6.country INNER JOIN
(SELECT MAX(city.population) AS pop, country_code
FROM lab6.city
GROUP BY country_code) AS sq
USING (country_code)
INNER JOIN
(SELECT city.name AS largest_city, city.population
FROM lab6.city) AS sq1
ON (sq1.population = sq.pop)
ORDER BY country.name ASC";
啊,我明白了。我對stackoverflow仍然陌生。謝謝。 – Bill