MySQL 双表 Join 双表答案

【问题标题】：MySQL Dual table Join Dual tableMySQL 双表 Join 双表
【发布时间】：2014-12-31 03:55:36
【问题描述】：

有没有办法从 MySQL 中的虚拟 DUAL 表中加入字段？

说我有一个

SELECT 1 as n1 FROM DUAL

n1
--
 1

还有一个

SELECT 2 as n2 FROM DUAL

n2
--
 2

我可以在某种查询中使用 Join 来连接两个选择吗...

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

【问题讨论】：

【解决方案1】：

这是一种方法...

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

还有一个

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;

你可以这样做

Select 1 as n1, 2 as n2

但我认为您需要连接是有原因的。

【讨论】：