Forum OpenACS Q&A: aggregate function calls may not be nested

I'm doing some "statistics" (in quotes because I couldn't calculate a standard deviation to save my life) on bills passed in our state legislature. I have two tables, "reps" (representatives) and bills:


bf2-new=# d reps
             Table "reps"
  Attribute  |     Type     | Modifier
-------------+--------------+----------
 id          | integer      | not null
 first_name  | varchar(200) | not null
 middle_name | varchar(200) |
 last_name   | varchar(200) | not null
 party       | varchar(20)  | not null
 title       | varchar(200) |
 elected_in  | integer      |
Index: reps_pkey
Constraint: ((party = 'R'::"varchar") OR (party = 'D'::"varchar"))

bf2-new=# d bills
                 Table "bills"
 Attribute |     Type     |      Modifier
-----------+--------------+--------------------
 id        | integer      | not null
 sub       | integer      | not null default 0
 rep_id    | integer      | not null
 title     | varchar(400) | not null
 passed    | integer      |
Index: bills_pkey
Constraint: ((passed = 0) OR (passed = 1))

Now, I want to get a comparison between how many bills a representative introduced and how many of them passed. (I thought perhaps a representative who focused on one or two bills would be more likely to make sure it "counted.") I tried (and failed) to come up with a good query for this, so I split it into two steps. First, a view on how many bills were introduced & passed by each representative:


create view bill_count_v as
select r.id as rep_id, count(*) as total, sum(passed) as passed
from reps r, bills b
where b.rep_id = r.id
group by r.id;

So far so good. Then the query:


select total as n_introduced, sum(total) as total, sum(passed) as 
passed,
       sum(passed)::float / sum(total) as percent
from bill_count_v
group by total;
bf2-new-# bf2-new-# bf2-new-# ERROR:  Aggregate function calls may 
not be nested

Doh!

It turns out that replacing "create view" with "create table" was fine for my purposes. But is there a better way to do this that I'm missing?