Sql，嵌套选择

Question

我正在学习如何在另一个选择中进行选择，我提供了一个解决方案，但它太长了。这个解决方案可以更短吗？

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

这样写：

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

谁能解释第二个查询，它是如何工作的，谢谢。

Answer 1

试试这个

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