alias problem on join

Hi folks,

I've got an accounts table and a transactions table and want to do a summary 
join.  If I do:

bank=# select aid, aname, aodraft from accounts a
bank-# left outer join (select account, sum(amount) as balance
bank(# from statement group by account) as s
bank-# on s.account = a.aid;

I get the results I want, but I need to rename the aid column to 'key' so that 
I can feed it into a standard routine I have in PHP to build a hash.  If I 
do:

bank=# select aid as key, aname, aodraft from accounts a
bank-# left outer join (select account, sum(amount) as balance
bank(# from statement group by account) as s
bank-# on s.account = a.key;

I get 

ERROR:  No such attribute or function 'key'

Any ideas why?

Also, I'm sure I can do this more efficiently as a single select/join, but 
can't seem to work out why (Friday morning syndrome).  Anyone give me a clue?
-- 
Gary Stainburn
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