什么是 MS Access SQL 相当于 FULL OUTER JOIN 与 a.key 是 NULL 和 b.key 是 NULL

Question

我想在 MS Access SQL 中执行的示例查询：

SELECT *
FROM TableA AS a
FULL OUTER JOIN TableB AS b
ON a.key = b.key
WHERE a.key IS NULL
OR b.key IS NULL

由于 MS Access SQL 不允许 FULL OUTER JOIN，我尝试使用下面的代码，但结果不正确。

SELECT *
FROM (TableA AS a
LEFT JOIN TableB AS b
ON a.key = b.key)
RIGHT JOIN TableB AS c
ON a.key = c.key
WHERE b.key IS NULL
OR a.key IS NULL

有谁知道如何构建我试图执行的上面示例查询的 MS Access SQL 等效项？

Answer 1

利用：

select . . . 
from a
where not exists (select 1 from b where b.key = a.key)
union all
select . . .
from b
where not exists (select 1 from a where a.key = b.key);

. . . . . . 用于您想要的列。

你可以使用*如果你使用：

select a.*, b.*
from a left join
     b
     on 1 = 0
where not exists (select 1 from b where b.key = a.key)
union all
select a.*, b.*
from b left join
     a
     on 1 = 0
where not exists (select 1 from a where a.key = b.key);