我應該避免重複引用視圖中的聚合列嗎？

所以我想總結一下我的業務應用程序中的賬戶餘額。我的（為我們的目的而簡化）數據模型如下所示：

--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)

我想創建一個視圖來為我總結餘額，所以我有這樣的東西：

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

我的問題與：

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

上面的線。我想像這樣引用聚合列兩次嗎？SQL Server 2k（不要讓我開始）是否足夠聰明，不會兩次將值相加？我有哪些選擇？

聚合只會計算一次，所以你沒問題。也就是說，我傾向於使用子查詢（根據@Aaron 的評論），但純粹是為了可讀性。

引用自：https://dba.stackexchange.com/questions/5581