也许是这样的。在CASE表达式中，使用“else 0”将避免空值和关于它们被消除的警告消息。

WITH MyTable as (
    SELECT * 
    FROM (
        VALUES
            ('1234', 12, 'AAA'),
            ('1234', 11, 'BBB'),
            ('1234', 10, 'CCC'),
            ('5678', 5, 'AAA'),
            ('4578', 10, 'AAA'),
            ('852', 8, 'AAA'),
            ('852', 9, 'BBB'),
            ('852', 10, 'CCC')
        ) t (item, qty, area) 
)
SELECT item, coalesce(sum(case when area = 'AAA' then qty else 0 end ) ,0) as 'AAA'
from MyTable
group by item 
having count(*) = 1

[编辑]这也行得通，但我认为戴尔的答案更好。

SELECT item, SUM(qty) as 'AAA'
from MyTable
group by item 
having count(*) = 1 AND MIN(area) = 'AAA'

使用NOT EXISTS检查同一item是否不存在其他area。

select item, qty, area
from MyTable mt1
where area = 'AAA'
and not exists (
    select 1
    from MyTable mt2
    where mt2.item = mt1.item and mt2.Area <> 'AAA'
);