SQL seclect整个用括号括起来后加一个字母

[Nitpicking]

跪求 如下两种表示的区别：
第一种表示 语法错误 SyntaxError: near 'A
第二种表示能输出正确结果



第一种表示：

select Customers.Name as Customers
from Customers,(select CustomerId from Orders)A
where Customers.Id not in A;

第二种表示

select Name as Customers 
from Customers 
where Id not in (select CustomerId from Orders)

[jark2008]

第二种表示是正确的语法，as Customers的含义是给Name加个别名Customers。

[Blue_Some]

第一种 select Customers.Name as Customers from Customers,(select CustomerId from Orders)A where Customers.Id not in A.CustomerId ; 逻辑不正确 select Customers.Name as Customers from Customers,(select CustomerId from Orders)A where Customers.Id = A.CustomerId ; 这样可以，你在外面再套个子查询还可以用用