Should I Avoid Repeated References to Aggregate Columns in a View? So I'm wanting to summarize the balance of the accounts in my business application.  My (simplified for our purposes) data model looks like:

--Main account table that holds the single accounts
create table account (
id int primary key,
descr varchar(50))

--This table holds the budgeted amount for the account.  This table also holds the
--'actual' adopted amount.  The difference is that budgeted is what they thought it
--should be, while adopted is what the board accepted.  They can be different
create table account_amount (
id int primary key,
acct_id int foreign key references account (id),
amount money,
type tinyint)

--Each monitary action against an account is contained here.  This is the transactional
--table
create table account_journal (
id int primary key,
acct_id int foreign key references account (id),
amount money)


I want to create a view to summarize the balance for me, so I've got something like this:

create view account_balance as
select a.id, isnull(aaBudgeted.amount,0) as budgeted, isnull(aaAlloted.amount,0) as alloted
, sum(isnull(aj.amount,0)) as journaled_activity,
, isnull(aaAlloted.amount,0) + sum(isnull(aj.amount,0)) as balance
from account a left join acct_amount aaBudgeted on a.id = aaBudgeted.acct_id
and aaBudgeted.type = 2
left join acct_amount aaAlloted on a.id = aaAlloted.acct_id
and aaAlloted.type = 1 and aaAlloted.is_current = 1
left join acct_journal aj on aj.acct_id = a.id
where a.fiscal_year = 2012
group by a.id, aaBudgeted.amount, aaAlloted.amount


My question has to with the:

isnull(aaAlloted.amount,0) + sum(isnull(aj.amount,0)) as balance


line above.  Do I want to be referencing an aggregate column twice like this?  Is SQL Server 2k (don't get me started) smart enough to NOT sum the values twice?  What are my options?
The aggregate will only be calculated once, so you're ok as you are. That said, I tend to use a subquery (as per @Aaron's comment) but purely for readability.