如何 select 每个国家/地区的最大邮政编码

Question

In each country, which city has the highest ZIP code? Select only the Country name, and the city name

这里有一个图解，可能对你有帮助：

这是我目前所做的：

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

如果有人能解决这个问题，我将不胜感激。

Answer 1

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

您也可以使用 row_number():

select co.countryname, ci.cityname, ci.zipcode
from country co
inner join (
    select ci.*, rank() over(partition by countryid order by zipcode desc) rn
    from city ci
) ci on ci.countryid = co.countryid

如果您是运行 MS Access，您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
)

Answer 2

你也可以试试这个。使用排名函数并在外部查询中对其进行过滤

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

如何 select 每个国家/地区的最大邮政编码

How to select biggest zip code for each country

sql

sql-server

database

greatest-n-per-group

lateral-join