postgresql - Finding group maxes in SQL join result

Two SQL tables. One contestant has many entries:

Contestants     Entries

Id   Name       Id  Contestant_Id  Score
--   ----       --  -------------  -----
1    Fred       1   3              100
2    Mary       2   3              22
3    Irving     3   1              888
4    Grizelda   4   4              123
                5   1              19
                6   3              50

Low score wins. Need to retrieve current best scores of all contestants ordered by score:

Best Entries Report
Name     Entry_Id  Score
----     --------  -----
Fred     5         19
Irving   2         22
Grizelda 4         123

I can certainly get this done with many queries. My question is whether there's a way to get the result with one, efficient SQL query. I can almost see how to do it with GROUP BY, but not quite.

In case it's relevant, the environment is Rails ActiveRecord and PostgreSQL.

Answer

Here is specific postgresql way of doing this:

SELECT DISTINCT ON (c.id) c.name, e.id, e.score
FROM Contestants c
JOIN Entries e ON c.id = e.Contestant_id
ORDER BY c.id, e.score

Details about DISTINCT ON are here.

My SQLFiddle with example.

UPD To order the results by score:

SELECT *
FROM (SELECT DISTINCT ON (c.id) c.name, e.id, e.score

      FROM Contestants c
      JOIN Entries e ON c.id = e.Contestant_id
      ORDER BY c.id, e.score) t
ORDER BY score