SQL查询选择每种类型之一

Question

假设我有这张表：

id colorName
1红色
2蓝色
3红色
4蓝色

如何选择每种颜色的一个代表？
结果：
1红色
2蓝色

Answer 1

不是随机代表，而是......

select color, min(id)
from   mytable
group by color;

Answer 2

select distinct colorname from mytable

Answer 3

在MS SQL Server和Oracle：

SELECT  id, colorName
FROM    (
        SELECT  id, colorName,
                ROW_NUMBER() OVER (PARTITION BY colorName ORDER BY id) AS rn
        FROM    colors
        ) q
WHERE   rn = 1

Answer 4

试试这个：

SELECT colorName,  
MIN(id) AS id  
FROM table  
GROUP BY colorname  

Answer 5

这是最简单的方法：

SELECT DISTINCT colorName FROM mytable ORDER BY colorName

Answer 6

SELECT DISTINCT colorname FROM yourtable ORDER BY id; （如果需要，将id更改为colorname）

或

SELECT colorname From yourtable GROUP BY colorname;