From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
---|---|
To: | Tatsuo Ishii <ishii(at)sraoss(dot)co(dot)jp> |
Cc: | andres(at)anarazel(dot)de, pgsql-general(at)postgresql(dot)org |
Subject: | Re: RowDescription message |
Date: | 2019-10-07 13:32:29 |
Message-ID: | 25427.1570455149@sss.pgh.pa.us |
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Lists: | pgsql-general |
Tatsuo Ishii <ishii(at)sraoss(dot)co(dot)jp> writes:
>>> According to the manualof RowDescription message
>>> https://www.postgresql.org/docs/12/protocol-message-formats.html
>>> Specifies the number of fields in a row (can be zero).
>>> Does 0 fields could actually happen?
>> Yes, e.g.:
>> SELECT;
> Thanks. Is it a valid SQL statement according to the standard?
See select.sgml:
<refsect2>
<title>Empty <literal>SELECT</literal> Lists</title>
<para>
The list of output expressions after <literal>SELECT</literal> can be
empty, producing a zero-column result table.
This is not valid syntax according to the SQL standard.
<productname>PostgreSQL</productname> allows it to be consistent with
allowing zero-column tables.
However, an empty list is not allowed when <literal>DISTINCT</literal> is used.
</para>
</refsect2>
regards, tom lane
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