Mondial DB內部查詢

Question

我試圖回答以下問題作爲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：

國家（代碼，名稱，資本，省，面積，人口）

市（名稱，國家，省，經度，緯度，人口）

到目前爲止，我有以下內容：

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; 

這是哪裏出錯了？

Answer 1

嘗試以這種方式（我增加了一個額外加入）

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

在原產地查詢由現場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