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

On 30/07/2025 23:34, Tom Lane wrote:
> PG Bug reporting form<noreply(at)postgresql(dot)org> writes:
>> SELECT 'John' AS nom,'James' AS nom
>> returns a table with attributes nom and nom that I can see in the output.
>> Returning a table that contains twice the same column should not be
>> permitted.
> There is pretty much zero chance that we will enforce that
> restriction. It would break too much application code.
> Also, it looks to me like there is no such requirement in
> the SQL standard.

Indeed.  In SQL:2023-1 (available free of charge at [1]) says in
Subclause 4.6, "Tables":

    "An operation that references zero or more base tables and returns
a table is called a *query*. The result of a query is called a *derived
table*."

and

    "Derived tables, other than viewed tables, may contain more than
one column with the same name."

So, not only is this not a bug we should fix, it is explicitly allowed
by the standard.

[1] https://www.iso.org/standard/76583.html

--

Vik Fearing