Postgres：SELECT AS不工作

Question

使用此查询我收到错误，无法弄清楚如何解决。

查询：

SELECT * FROM (
      (SELECT 1), (SELECT  2) 
     )

错误：

syntax error at or near ","

Answer 1

你有额外的括号。我也建议使用别名：

SELECT *
FROM (SELECT 1 as a) x CROSS JOIN
     (SELECT 2 as b) y;

或者子查询只返回一行和一列：

SELECT (SELECT 1), (SELECT 2);