问题描述
我不小心写了一个查询，例如my_table中的 select; ，令人惊讶的是它是有效的语句。对我来说更有趣的是，即使 SELECT; 在PostgreSQL中也是有效的查询。您可以尝试使用以下代码编写很多有趣的查询：
I accidently wrote a query like select from my_table; and surprisingly it is valid statement. Even more interesting to me is that even SELECT; is a valid query in PostgreSQL. You can try to write a lot funny queries with this:
select union all select;
with t as (select) select;
select from (select) a, (select) b;
select where exists (select);
create table a (b int); with t as (select) insert into a (select from t);
这是某种定义SQL标准的结果，还是有一定的用例？
Is this a consequence of some definition SQL standard, or there is some use case for it, or it is just funny behavior that no one cared to programatically restrict?
推荐答案
如果我没有记错的话，零列表的可能性是表继承的副作用。在Postgres邮件列表中对此进行了讨论（但我现在找不到它们）
The possibility of "zero-column" tables is a side effect of the table inheritance if I'm not mistaken. There were discussions over this on the Postgres mailing lists (but I can't find them right now)
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