在select子句中进行子选择并使用其值

Question

有一种方法可以返回依赖于该字段的子选择和返回操作吗？

例如，我可以这样做：

select a, (select top 1 b from b) as b, (a * b) as c
from a

Answer 1

select a, b, (a * b) as c
from (
    select a, (select top 1 b from b) as b
    from a
) x

Answer 2

将子查询放在from子句中：

select a.a, b.b, (a.a * b.b) as c
from a cross join
     (select top 1 b from b) b;