如何排除SQL查詢結果

Question

我有兩個表，每個表都有一列product_id ，我想做一個查詢，該查詢將排除兩個表中都有product_id產品的結果。

偽示例：

SELECT *
FROM table1
WHERE product_id NOT IN table2

Answer 1

如果兩個表中都可以有product_id，而另一個表中不存在，則必須進行聯合，因為mysql不支持完全外部聯接：

select t1.product_id, 't1' as table_name
from table1 t1 left join table2 t2
on t1.product_id = t2.product_id where t2.product_id is null 
union
select t2.product_id, 't2' as table_name
from table1 t1 right join table2 t2
on t1.product_id = t2.product_id where t1.product_id is null     

Answer 2

嘗試這個：

select * from table1 
where product_id not in (select product_id from table2) as p;