这个 with 关键字只应在查询开头出现一次：

WITH 
    T1 as ( SELECT something as s1 from schema1.table1 ),
    T2 as ( SELECT something as s2 from schema2.table1 )
SELECT T1.something something1, T2.something something2
FROM T1
CROSS JOIN T2;

注意，我将隐式连接重写为显式连接 cross join . 您可能还应该在resultset中为列名起别名，因为两个查询都会生成一个名称相同的列。

你到底想要什么？
两个表的笛卡尔积
第一个表的所有行，第二个表的所有行？
我在with子句中放置了一些示例数据（是的，with关键字只有一次，然后是一个逗号列表），并显示了两个结果。你的，首先（我同意@gmb，你应该使用它） CROSS JOIN 如果将两个表连接起来（没有筛选器），那么我认为更有意义。
来吧。

-- the WITH clause ...
WITH
table1(id,something) AS (
          SELECT 11,'something 1 from 1'
UNION ALL SELECT 12,'something 2 from 1'
UNION ALL SELECT 13,'something 3 from 1'
)
,
table2(id,something) AS (
          SELECT 21,'something 1 from 2'
UNION ALL SELECT 22,'something 2 from 2'
UNION ALL SELECT 23,'something 3 from 2'
)

--然后，我从中选择，就像你会得到的结果一样：

SELECT * FROM table1,table2
 id |     something      | id |     something      
----+--------------------+----+--------------------
 11 | something 1 from 1 | 21 | something 1 from 2
 12 | something 2 from 1 | 21 | something 1 from 2
 13 | something 3 from 1 | 21 | something 1 from 2
 11 | something 1 from 1 | 22 | something 2 from 2
 12 | something 2 from 1 | 22 | something 2 from 2
 13 | something 3 from 1 | 22 | something 2 from 2
 11 | something 1 from 1 | 23 | something 3 from 2
 12 | something 2 from 1 | 23 | something 3 from 2
 13 | something 3 from 1 | 23 | something 3 from 2

--最后，我几乎肯定你应该做的是：

SELECT * FROM table1 UNION ALL SELECT * FROM table2;
  id |     something      
 ----+--------------------
  11 | something 1 from 1
  12 | something 2 from 1
  13 | something 3 from 1
  21 | something 1 from 2
  22 | something 2 from 2
  23 | something 3 from 2