如何获取0作为计数输出？

kxe2p93d 于 2021-08-09 发布在 Java

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SELECT Country.NAME, COUNT(City.NAME) as Number_of_cities
FROM City
JOIN Country ON City.COUNTRY = Country.CODE
WHERE City.LONGITUDE IS NULL AND City.LATITUDE IS NULL
GROUP BY Country.NAME, City.COUNTRY;

就像现在的代码一样，没有显示那些只有长宽值城市的国家。我该如何更改代码，以便所有城市都有长距离和纬度值的国家将0显示为coun？

sql count Database

来源：https://stackoverflow.com/questions/62138425/how-to-get-0-as-a-count-output

1条答案

按热度按时间

xhv8bpkk1#

你想要一个 left join ，在 on 条款：

SELECT co.NAME, COUNT(ci.country) as Number_of_cities
FROM country co left join
     City ci
     ON ci.COUNTRY = co.CODE and
        ci.LONGITUDE IS NULL and
        ci.LATITUDE IS NULL
GROUP BY co.NAME;

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如何获取0作为计数输出？

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