Re: RowDescription message

Tatsuo Ishii <ishii@sraoss.co.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