Unlike Oracle and Microsoft SQL Server 2005, PostgreSQL offers no built-in function to dynamically rank rows. However, one can use the MSDN article, How to dynamically number rows in a SELECT Transact-SQL statement, as a basis for developing techniques that do work in PostgreSQL. This article assumes that there exists a table named players, containing two columns, player_id and score.

The first technique is the simplest to understand, but requires the use of a temporary sequencer. If sequencer functionality is not available in your database, then this technique cannot be utilitized:

CREATE TEMPORARY SEQUENCE rank_seq; 
SELECT player_id, score, nextval('rank_seq') AS rank FROM 
    (SELECT * FROM players ORDER BY score DESC) as p1 
ORDER BY rank

The second technique uses a subselect statement to rank its result. This can be computationally expense because of the COUNT operation within the subselect statement:

SELECT 
    player_id, score, 
    (SELECT COUNT(*) FROM players p2 
    WHERE p2.score > p1.score) + 1 AS rank 
FROM
    players p1 
ORDER BY score DESC

The third and final technique uses a self-join operation. It is ideal for environments on lightweight databases where the subselect statement is available. Unfortunately, this technique is also the least intuitive of the three. I recommend running this query piecewise in a query browser to understand how the individual components fit together:

SELECT
   p1.player_id, p1.score, COUNT(p2.player_id) AS rank 
FROM 
   players p1, players p2 
WHERE 
  p2.score >= p1.score 
GROUP BY 
  p1.player_id, p1.score 
ORDER BY rank