簡單的MySQL的聯接不工作的權利

我簡單的MySQL的聯接不工作的權利

SELECT country.* , COUNT(country.coid) AS city_count_for_country 
FROM `air_countries` AS country 
JOIN `air_cities` AS city ON city.coid = country.coid

但它返回只是一個國家，city_count_for_country不計爲一個國家的所有城市，但剛纔的所有城市。怎麼了？

感謝

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2011-12-06 Raimonds

你想要的是僅由group by關鍵字實現;單獨從不聚合行;你可能想通過添加到您的查詢

GROUP BY country.coid

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2011-12-06 14:29:21 codeling

你需要它組

SELECT country.* , COUNT(country.coid) AS city_count_for_country 
FROM `air_countries` AS country 
JOIN `air_cities` AS city ON city.coid = country.coid 
GROUP BY country.coid

來源

2011-12-06 14:29:04 Flukey

嘗試。試試這個：

select country.coid, count(*) as city_count_for_country 
from `air_countries` as country 
join `air_cities` as city on city.coid = country.coid 
group by country.coid;

來源

2011-12-06 14:30:22 DigitalWM

你缺少GROUP BY條款使用分組功能，寫

SELECT country.* , COUNT(country.coid) AS city_count_for_country 
    FROM air_countries AS country 
    JOIN air_cities AS city 
    ON city.coid = country.coid 
    GROUP BY country.coid

來源

2011-12-06 14:30:30

簡單的MySQL的聯接不工作的權利

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