关于Group by 的一个问题

[wangweilie]

我想将orderDate算出的year作为分组的字段，sql语句如下：
select year(orderDate) as a, sum(freight) from orders group by a

其中ordreDate 是 datetime 字段类型

但提示以下错误
服务器: 消息 207，级别 16，状态 3，行 1
列名 'a' 无效。
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求各位高手，有何SQL语句能满足我的要求。

[heixiu1980]

select year(orderdate) as a,sum(freight) from orders
group by year(orderdate)

[愉快的登山者]

select year(orderdate) 年度, sum(freight) 合计 from orders
group by year(orderdate)
order by year(orderdate)

[CrazyFor]

select year(orderDate) as a, sum(freight) from orders group by year(orderDate)