-----Original Message-----
From: Tom Lane <tgl@sss.pgh.pa.us>
Sent: Thursday, July 25, 2019 2:47 PM
To: Adrian Klaver <adrian.klaver@aklaver.com>
Cc: Kevin Brannen <KBrannen@efji.com>; pgsql-generallists.postgresql.org <pgsql-general@lists.postgresql.org>
Subject: Re: SELECT INTO question
Adrian Klaver <adrian.klaver@aklaver.com> writes:
> On 7/25/19 12:23 PM, Kevin Brannen wrote:
>> We're trying to understand what happened with a SELECT INTO. The
>> problem can be see with this example:
>>
>> nms=# select into t2 from t1;
>> SELECT 5
>> # select * from t2;
>> --
>> (5 rows)
> The list of output expressions after SELECT can be empty, producing a
> zero-column result table. This is not valid syntax according to the
> SQL standard. PostgreSQL allows it to be consistent with allowing
> zero-column tables. However, an empty list is not allowed when
> DISTINCT is used.
Right, you selected no columns from t1, so t2 has no columns (and yet five rows). Worth noting here is that psql is a bit squirrely about displaying zero-column results --- it drops the column-names header line, and it doesn't emit a blank-line-per-row as one might expect.
Perhaps somebody ought to fix that, but it's such a corner case that no one has bothered yet.
Hmm, I don't particularly like that answer as I'd have preferred a "syntax error", but I do understand it.
Thanks for the answer, Adrian; and thanks for the expansion, Tom.
Kevin
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