Re: BUG #19003: A SELECT that does not return a valid table

On Wed, Jul 30, 2025, 12:50 PG Bug reporting form <noreply(at)postgresql(dot)org>
wrote:

> The following bug has been logged on the website:
>
> Bug reference: 19003
> Logged by: Alexandre Bailly
> Email address: alexandrebailly1955(at)gmail(dot)com
> PostgreSQL version: 17.5
> Operating system: Windows
> Description:
>
> Returning a table that contains twice the same column should not be
> permitted. It should be a nice mathematical property (closure) if a SELECT
> always returns a valid table.
>
>
This isn't a bug. And at this point, regardless of such purity concerns,
there is no way we are going to change this behavior and break
well-functioning applications.

A query result is not a table. It just has a tabular form (rows and
columns). It is also not a set though set-theory did inspire various
aspects of SQL.

David J.