Re: BUG #17408: Duplicate aliases silently fail

On Wed, Feb 16, 2022 at 5:46 PM PG Bug reporting form
<noreply@postgresql.org> wrote:

> Assigning aliases to columns works perfectly.
>
> eg. "SELECT name AS customer_name FROM customers"
>
> However you are able to assign duplicate aliases which does not cause a
> conflict
>
> eg. "SELECT name AS customer_name, surname AS customer_name FROM
> customers"
>
> The expectation here is that duplicate aliases would cause the query to fail
> due to duplicate column names in the result, however there is no error or
> warning.

FWIW, if the aliases are referenced higher up in a query, it does
result in error:

WITH dupe_cols AS (SELECT name AS customer_name, surname AS customer_name FROM
customers) SELECT customer_name FROM dupe_cols;
ERROR:  column reference "customer_name" is ambiguous
LINE 2: customers) select customer_name from dupe_cols;

-- 
John Naylor
EDB: http://www.enterprisedb.com