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

On Wed, Jul 30, 2025, 12:50 PG Bug reporting form <noreply@postgresql.org>
wrote:

> The following bug has been logged on the website:
>
> Bug reference:      19003
> Logged by:          Alexandre Bailly
> Email address:      alexandrebailly1955@gmail.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.