带有语法错误的 PostgreSQL 子查询给出了有效的结果 [英] PostgreSQL subquery with syntax error gives a valid result

问题描述

这里发生了什么?

我有两个表，test1 和 test2:

I got two tables, test1 and test2:

create table test1 (id1 int4 primary key);
create table test2 (id2 int4 primary key);

正如预期的那样，这个查询:

As expected, this query:

select id1 from test2;

产生语法错误:

ERROR:  column "id1" does not exist
LINE 1: select id1 from test2;

但是，当我尝试执行此查询时:

However, when I try to execute this query:

select * from test1 where id1 in (select id1 from test2);

PostgreSQL 不抱怨，执行查询并给我:

PostgreSQL doesn't complain, executes the query and gives me:

 id1
-----
(0 rows)

这有什么逻辑吗?还是我应该提交错误报告?

Is there any logic in this? Or should I file a bug report?

推荐答案

来自外部 select 的列在子选择中可见.

Columns from outer select are visible in sub-select.

您的查询相当于:

select * 
from test1 
where test1.id1 in (select test1.id1 from test2);

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