三重联接SQL

Question

如何在SQL中获得以下维恩图的红色部分

感谢您的帮助！

Answer 1

我会首先想到except：

select c.*
from c
except
select a.*
from a
except 
select b.*
from b;

我的下一个想法是not exists：

select c.*
from t
where not exists (select 1 from a where a.id = c.id) and
      not exists (select 1 from b where b.id = c.id);

Answer 2

使用Joins，您可以获取Ven图的任何部分，具体情况如下所示。

select c.* 
from TableC c
left join TableA a on a.id = c.id 
left join TableB b on b.id = c.id
Where a.id is null and b.id is null -- Records which does not match in both tables

Answer 3

考虑到您没有给出实际的表结构，而是类似这样的事情，将会有些麻烦：

Select c.name
From c
Where not exists (select 1 from b where b.id = c.id)
  And not exists (select 1 from a where a.id = c.id);

Answer 4

您可以使用NOT IN（假设id是常用属性）：

SELECT c.id FROM c 
WHERE c.id NOT IN (SELECT a.id FROM a)
AND c.id NOT IN (SELECT b.id FROM b);