Mondial DB内部查询

Question

我试图回答以下问题作为Mondial DB的一部分。

-- For each country display the city with the highest population together with the number of the population. 

的表是：

国家（代码，名称，资本，省，面积，人口）

市（名称，国家，省，经度，纬度，人口）

到目前为止，我有以下内容：

SELECT 
    Country.Name, MaxCity.CityName, MaxCity.Population 
FROM 
    (SELECT 
     MAX(Population) AS Population, 
      City.Country, 
      City.Name AS CityName 
    FROM 
     City 
    GROUP BY City.Country) AS MaxCity 
     JOIN 
    Country ON Country.Code = MaxCity.Country; 

这是哪里出错了？

Answer 1

尝试以这种方式（我增加了一个额外加入）

SELECT 
    Country.Name, City.CityName, City.Population 
FROM 
    Country Join City On Country.Code = City.Country 
Join (SELECT 
     MAX(Population) AS Population,Country as Country from City Group By Country) as X 
On City.Country = x.Country and City.Population = x.Population 

Answer 2

在原产地查询由现场city.name

select country.name, maxcity.cityname, maxcity.population 
    from 
     (select 
      MAX(population) as population, 
     city.country, 
     city.name as cityname 
    from city 
    group by city.country, city.name) as maxcity 
      join 
    country on country.code = maxcity.country