From: Tom Lane <tgl@sss.pgh.pa.us>
To: Subodh Kumar <subodh.kumar@epps-erp.com>
cc: pgsql-admin@lists.postgresql.org
Subject: Re: creating table without columns
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Comments: In-reply-to Subodh Kumar <subodh.kumar@epps-erp.com>
	message dated "Tue, 30 Oct 2018 17:22:29 +0530"
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Date: Tue, 30 Oct 2018 09:12:43 -0400
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Subodh Kumar <subodh.kumar@epps-erp.com> writes:
> I have run below query it is created 'test' table without columns
> but table row count is 2.
> please give me clarity about this, i thought it may give syntax error but
> not
> either it must have 2 rows data but both are not happened.

> with ins_test as (select 1 as srno
> union
> select 2)
> select into test from ins_test;

I think you meant to write

with ins_test as (select 1 as srno
union
select 2)
select * into test from ins_test;

or possibly

with ins_test as (select 1 as srno
union
select 2)
select srno into test from ins_test;

What you did write has no columns in the SELECT result clause,
so the INTO creates a table of no columns --- but you get
the expected number of rows.

Postgres allows zero-column tables, and zero-column selects,
because otherwise there are too many weird corner cases;
for instance ALTER TABLE DROP COLUMN would have to reject
dropping the last column.  The SQL standard has a different
opinion about which way is less ugly ...

			regards, tom lane