MySQL - 选择按字母顺序排列的名字

Question

我已经开始学习MySQL了。

下面是表world：

+-------------+-----------+---------+ 
| name  | continent | area | 
+-------------+-----------+---------+ 
| Afghanistan | Asia  | 652230 | 
| Albania  | Europe | 2831741 | 
| Algeria  | Africa | 28748 | 
| ...   | ...  | ...  | 
+-------------+-----------+---------+ 

我需要：

每个大洲和国家的自带首字母顺序排列

SELECT的结果必须名单成为：

+---------------+---------------------+ 
| continent |   name  | 
+---------------+---------------------+ 
| Africa  | Algeria    | 
| Asia   | Afghanistan   | 
| Caribbean  | Antigua and Barbuda | 
| Eurasia  | Armenia    | 
| Europe  | Albania    | 
| North America | Belize    | 
| Oceania  | Australia   | 
| South America | Argentina   | 
+---------------+---------------------+ 

Answer 1

这是一个简单aggegation：

SELECT continent, MIN(name) AS name 
FROM world 
GROUP BY continent 
ORDER by continent 

Answer 2

试试这个

select distinct w.continent, 
       (select w2.name 
        from world w2 
        where w.continent = w2.continent 
        order by name asc 
        limit 1) name 
from world w 
order by w.continent 

Answer 3

试试这个

SELECT continent, name FROM world ORDER BY name ASC; 

Answer 4

如果你需要列出每个大洲按字母顺序，你必须使用

 SELECT * from world ORDER by continent 

但是，如果你NEDD列表中的每个国家的有使用

 SELECT * from world ORDER by name 

Answer 5

如果是从SQLZoo练习，比IMO就应该是这个样子：

select continent, name from world x 
where name = (select name 
        from world y 
        where x.continent = y.continent 
        order by name asc 
        limit 1) 

附：我从那里学习SQL，这篇文章帮助了我。感谢@Parado！）

更新：我找到了site的答案。如果堆栈很有用。

Answer 6

select continent, name from world group by continent order by name 

Answer 7

的SqlZoo解决方案将能更好地看起来像这样：

SELECT continent, name FROM world x 
WHERE name <= ALL 
    (SELECT name FROM world y WHERE y.continent=x.continent) 

Answer 8

你看这个SQL：

select distinct continent, 
     (select name 
     from world y where y.continent = x.continent limit 1) as name 
from world x 

Answer 9

SELECT distinct x.continent , x.name 
FROM world x ,world y 
WHERE x.name = (SELECT y.name FROM world y 
WHERE y.continent=x.continent order by y.name asc limit 1) ; 

Answer 10

SELECT continent, 
     name 
FROM world x 
WHERE name= 
    (SELECT name 
    FROM world y 
    WHERE x.continent=y.continent 
    ORDER BY name 
    LIMIT 1) 

这是关联/同步查询。