MySQL雙表加入雙表

Question

有沒有辦法從MySQL的虛擬DUAL表中加入字段？

說我有一個

SELECT 1 as n1 FROM DUAL 

n1 
-- 
1 

和

SELECT 2 as n2 FROM DUAL 

n2 
-- 
2 

我能加入一個都選擇加入某種查詢爲...

SELECT 1 as n1 FROM DUAL JOIN (SELECT 2 as n2 FROM DUAL) ON 1=1 

？

Answer 1

這裏有一種方法......

Select t1.n1, t2.n2 
from (select 1 as n1) t1 
CROSS JOIN (Select 2 as n2) t2; 

這裏的另一個

Select t1.n1, t2.n2 
from (select 1 as n1, 'A' as ID) t1 
INNER JOIN (Select 2 as n2, 'A' as ID) t2 
    on T1.Id = T2.ID; 

，你可以只是做

Select 1 as n1, 2 as n2 

但我相信有您需要的加入的原因。