SELECT my_table.varchar FROM my_table

On Mon, May 31, 2010 at 7:48 AM, Jan Strube <js@deriva.de> wrote:

I accidentally encountered a feature in Postgres 8.3 that I couldn't find in
the documentation while submitting a query like

SELECT my_table.varchar FROM my_table

which returns a concatenated string of all field values per row.
I wonder where this is documented (and if it has something to do with
composite types).

Can anyone please explain?

I don't really know, but the result looks more like a single field
formatted as "ROW-WISE" rather than CSV. The official way to get this
result is:

SELECT ROW( my_table.* ) FROM my_table;

http://www.postgresql.org/docs/9.0/static/sql-expressions.html#SQL-SYNTAX-ROW-CONSTRUCTORS

--
Regards,
Richard Broersma Jr.

Visit the Los Angeles PostgreSQL Users Group (LAPUG)
http://pugs.postgresql.org/lapug

Richard Broersma <richard.broersma@gmail.com> writes:

On Mon, May 31, 2010 at 7:48 AM, Jan Strube <js@deriva.de> wrote:

I accidentally encountered a feature in Postgres 8.3 that I couldn't find in
the documentation while submitting a query like

SELECT my_table.varchar FROM my_table

which returns a concatenated string of all field values per row.
I wonder where this is documented (and if it has something to do with
composite types).

Can anyone please explain?

I don't really know, but the result looks more like a single field

It's equivalent to (my_table.*)::varchar. We've seen enough people
confused by this (or the equivalent cases with text and name as
the target type) that I wonder if we should intentionally break the
symmetry and disable treating this case as a cast. Although I do
rather wonder what the OP expected to happen here.

regards, tom lane

Am 31.05.2010 17:44, schrieb Tom Lane:

Richard Broersma<richard.broersma@gmail.com> writes:

On Mon, May 31, 2010 at 7:48 AM, Jan Strube<js@deriva.de> wrote:

I accidentally encountered a feature in Postgres 8.3 that I couldn't find in
the documentation while submitting a query like

SELECT my_table.varchar FROM my_table

which returns a concatenated string of all field values per row.
I wonder where this is documented (and if it has something to do with
composite types).

Can anyone please explain?

I don't really know, but the result looks more like a single field

It's equivalent to (my_table.*)::varchar. We've seen enough people
confused by this (or the equivalent cases with text and name as
the target type) that I wonder if we should intentionally break the
symmetry and disable treating this case as a cast. Although I do
rather wonder what the OP expected to happen here.

I didn't expect anything special, because my original statement was
actually a typo. So I was just amazed that I didn't get an error.

Thanks for the explanation,
Jan