SQL query to select one of each kind

Question

Let's say I have this table:

id colorName
1 red
2 blue
3 red
4 blue

How to select one representative of each color? Result:
1 red
2 blue

Thanks.

Answer 1

Not random representatives, but...

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

Answer 2

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

Answer 3

select distinct colorname from mytable

Answer 4

In MS SQL Server and Oracle:

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