Sql 如何为每个国家选择最大的邮政编码

在每个国家，哪个城市的邮政编码最高？ 仅选择国家名称和城市名称

以下是一个图形模式，可以帮助您：

这就是我到目前为止所做的：

SELECT CountryName, CityName
from City ci
join County co on co.CountryID = ci.CountryID
group by CountryName, CityName, ci.ZipCode
having ZipCode = MAX(ZipCode)

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如果有人能帮我解决这个问题，我将不胜感激。

一个选项使用横向连接：

select co.countryname, ci.cityname, ci.zipcode
from country co
cross apply (
    select top (1) with ties ci.* 
    from city ci 
    where ci.countryid = co.countryid
    order by ci.zipcode desc
) ci

您还可以使用

行编号（）

：

如果正在运行MS Access，则可以使用相关子查询：

select co.countryname, ci.cityname, ci.zipcode
from country co as co
inner join city as ci on ci.countryid = co.countryid
where ci.zipcode = (
    select max(c1.zipcode)
    from city as ci1
    where ci1.countryid = ci.country
)

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你也可以试试这个。使用秩函数并在外部查询中对其进行拟合

select * from
(select c1.countryname as countryname, c2.cityname as cityname, 
max_city_zip = rank() Over (partition by c1.countryname order by c2.cityname desc)
from country c1
inner join city c2
on c1.countryID = c2.countryID
group by c1.countryname, c2.cityname)Y where max_city_zip = 1

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您使用的是SQL Server还是MS Access？请移除其中一个标签。请同时显示（以文本格式而不是图像）一些示例数据和预期结果。SQL Server（Transact-SQL）我将尝试从GROUP BY子句中删除ci.zipcode，因为您正在尝试查找最大值。如果将其包含在GROUP BY中，则将获得所有zipcode。

select * from
(select c1.countryname as countryname, c2.cityname as cityname, 
max_city_zip = rank() Over (partition by c1.countryname order by c2.cityname desc)
from country c1
inner join city c2
on c1.countryID = c2.countryID
group by c1.countryname, c2.cityname)Y where max_city_zip = 1