Re: postgres question: Views with duplicate field names

On 09/05/2016 01:13 PM, Ryan Murphy wrote:
> Interesting, thanks!  Do you know why the first one fails instead of
> doing that renaming process, while your version succeeds?

Because I specifically aliased the first task reference using AS task_1.

>
> On Monday, September 5, 2016, Adrian Klaver <adrian.klaver@aklaver.com
> <mailto:adrian.klaver@aklaver.com>> wrote:
>
>     On 09/05/2016 12:55 PM, Ryan Murphy wrote:
>
>         Hello, I have a question about views in Postgres.
>
>         Given a table like so:
>
>         create table todo (
>           id serial,
>           task text,
>           done_time timestamp default null
>         );
>
>         it is legal (though perhaps not advised, by some) to query it
>         like so:
>
>         select task, * from todo;
>
>         This gives a result with 2 redundant "task" fields (with
>         duplicate names):
>
>              task     | id |     task     | done_time
>         --------------+----+--------------+-----------
>          wash the dog |  1 | wash the dog |
>
>         However, if I try to make a view of this I hit a problem: views
>         can't
>         have duplicate field names:
>
>         create view task2 as   select task, * from todo;
>
>         ERROR:  column "task" specified more than once
>
>         I understand this may seem like a silly thing to want to do, but my
>         question is if there is an easy way to automatically de-dup the
>         columns
>         of the query so I can create a view from it.  Or is there any
>         fundamental reason why views can't be allowed to have duplicate
>         columns,
>         just like the result set above?
>
>
>     test=> create view task2 as   select task AS task_1 , * from todo;
>     CREATE VIEW
>
>     test=> \d task2
>                      View "public.task2"
>
>       Column   |            Type             | Modifiers
>
>     -----------+-----------------------------+-----------
>
>      task_1    | text                        |
>
>      id        | integer                     |
>      task      | text                        |
>      done_time | timestamp without time zone |
>
>
>
>         Thanks!
>
>         Ryan
>
>
>
>     --
>     Adrian Klaver
>     adrian.klaver@aklaver.com
>


--
Adrian Klaver
adrian.klaver@aklaver.com