Обсуждение: Postgres and alias

Hi, I am migrating a database from Sybase to PostgreSql 12.

This select in sybase works for me, but with postgresql it accuses me
"THERE IS NO COLUMN ls_numero"

select '1234567890' as ls_number,
                   substr (ls_number, 3, 3);

Is it possible to get information from an alias in postgresql? how would the
code be?

Hmm, how about:

SELECT substr (ls_number, 3, 3)
FROM (VALUES('1234567890')) as t(ls_number);

St.

> On 27 Aug 2020, at 18:55, Fontana Daniel C (Desartec S.R.L.) <desartecsrl@gmail.com> wrote:
>
> Hi, I am migrating a database from Sybase to PostgreSql 12.
>
> This select in sybase works for me, but with postgresql it accuses me
> "THERE IS NO COLUMN ls_numero"
>
> select '1234567890' as ls_number,
>                  substr (ls_number, 3, 3);
>
> Is it possible to get information from an alias in postgresql? how would the
> code be?
>
>
>
>

Hi Daniel,

> On 27. Aug, 2020, at 17:55, Fontana Daniel C (Desartec S.R.L.) <desartecsrl@gmail.com> wrote:
>
> Hi, I am migrating a database from Sybase to PostgreSql 12.
>
> This select in sybase works for me, but with postgresql it accuses me
> "THERE IS NO COLUMN ls_numero"
>
> select '1234567890' as ls_number,
>                   substr (ls_number, 3, 3);
>
> Is it possible to get information from an alias in postgresql? how would the
> code be?

try this:

postgres=# select ls_number, substr (ls_number, 3, 3) from (select '1234567890' as ls_number) a;
 ls_number  | substr
------------+--------
 1234567890 | 345
(1 row)

Cheers,
Paul

Perfect.

now let's imagine that '1234567890' is a function f_art_get_price(id_code),
which returns in a string like the following 'XXXZMMM1234567890123yyyy/mm/dd'
where 1234567890123 is the price and yyyy/mm/dd the date it was last changed price.
How would you do in this case to obtain these values ​​separately?
without calling the function 2 times avoiding overloading the base?

something like this

select art.description,
     f_art_get_price_str( art.id ) as ls_price_and_date
    SUBSTRING( ls_price_and_date, 7, 13 )
from articulos;

-----Mensaje original-----
De: Stelios Sfakianakis [mailto:sgsfak@gmail.com]
Enviado el: jueves, 27 de agosto de 2020 12:59
Para: Fontana Daniel C (Desartec S.R.L.)
CC: pgsql-general@lists.postgresql.org
Asunto: Re: Postgres and alias

Hmm, how about:

SELECT substr (ls_number, 3, 3)
FROM (VALUES('1234567890')) as t(ls_number);

St.

> On 27 Aug 2020, at 18:55, Fontana Daniel C (Desartec S.R.L.) <desartecsrl@gmail.com> wrote:
>
> Hi, I am migrating a database from Sybase to PostgreSql 12.
>
> This select in sybase works for me, but with postgresql it accuses me
> "THERE IS NO COLUMN ls_numero"
>
> select '1234567890' as ls_number,
>                  substr (ls_number, 3, 3);
>
> Is it possible to get information from an alias in postgresql? how
> would the code be?
>
>
>
>

> On 28 Aug 2020, at 2:14, Fontana Daniel C (Desartec S.R.L.) <desartecsrl@gmail.com> wrote:
>
> Perfect.
>
> now let's imagine that '1234567890' is a function f_art_get_price(id_code),
> which returns in a string like the following 'XXXZMMM1234567890123yyyy/mm/dd'
> where 1234567890123 is the price and yyyy/mm/dd the date it was last changed price.
> How would you do in this case to obtain these values ​​separately?
> without calling the function 2 times avoiding overloading the base?
>
> something like this
>
> select art.description,
>      f_art_get_price_str( art.id ) as ls_price_and_date
>     SUBSTRING( ls_price_and_date, 7, 13 )
> from articulos;

Let's assume art is supposed to be an alias for articulos.
Something like this?:

select art.description,
    p.ls_price_and_date,
    SUBSTRING( p.ls_price_and_date, 7, 13 )
from articulos art
cross join lateral f_art_get_price_str( art.id ) p(ls_price_and_date);


Alban Hertroys
--
There is always an exception to always.