SQL处理顺序

Question

考虑我有一个查询

select * from A
Except 
select * from B 
union all
select * from B 
except
select * from A

查询处理如下

select * 
from 
(
select * from A
Except 
select * from B 
) a
union all
(
select * from B
Except 
select * from A 
) b

如何在sql中定义处理顺序.在任何情况下它都会这样处理吗？

select * from A
Except 
select * from
(
select * from B 
union all
select * from B 
) a
except
select * from A

Answer 1

EXCEPT和UNION"从左到右"处理.这意味着没有任何括号来确定它们将按照它们出现在sql中的顺序进行处理.