Is it possible to use a column value as the argument to a hypothetical-set aggregate function? Say I have a table like the one described below.

                                     Table "public.foo"
  Column   |            Type             |                    Modifiers                 
-----------+-----------------------------+-------------------------------------------------
 id        | integer                     | not null default nextval('foo_id_seq'::regclass)
 data      | text                        | not null
 score     | integer                     |


To calculate the percentile rank for a particular score, I can do something like this:

test=# select percent_rank(5) within group (order by score) as rank from foo;
        rank     
--------------------
 0.0762917366163029
(1 row)


What I'd really like to do is have a select statement that shows the data, score, and rank for each row present. I tried the below query.

test=# select data, score, percent_rank(score) within group (order by score) as rank from foo group by data, score;


This produces a rank of 0 for every row. I'm assuming this is because the within group clause ends up being limited by group by clause, but I'm not enough of a SQL ninja to know for sure.

At any rate, is it possible to include the percentile rank of a row's score as part of a multi-row select?
If you include ID I would assume that you can join it back to itself on ID to get that information in one dataset.