SQL，嵌套选择

问题描述

我正在学习如何在另一个选择中进行选择，并且提供了解决方案，但是时间太长了。这个解决方案可以缩短吗？

我想要这个查询：

    select continent,name 
from world x
where name =
    (SELECT min(name) FROM world
        WHERE continent = 'Africa')
or name =
    (SELECT min(name) FROM world
        WHERE continent = 'Asia')
or name =
    (SELECT min(name) FROM world
        WHERE continent = 'Caribbean')
or name =
    (SELECT min(name) FROM world
        WHERE continent = 'Eurasia')
or name =
    (SELECT min(name) FROM world
        WHERE continent = 'Europe')
or name =
    (SELECT min(name) FROM world
        WHERE continent = 'north America')
or name =
    (SELECT min(name) FROM world
        WHERE continent = 'Oceania')
or name =
    (SELECT min(name) FROM world
        WHERE continent = 'South America')
order by continent
limit 8

以这样的方式写：

    SELECT continent,name,area FROM world x
  WHERE area >= ALL
    (SELECT max(area) FROM world y
        WHERE y.continent = x.continent
          AND area > 0)

任何人都可以解释第二个查询，它如何工作，谢谢。

解决方法

尝试一下

SELECT Continent,Name 
FROM World x
WHERE NAME IN (SELECT MIN(Name) FROM world WHERE Continent IN ('Africa','Asia','Caribbean','Eurasia','Europe','North America','Oceania','South America') GROUP BY Continent)
ORDER BY Continent
LIMIT 8