Re: Postgres and alias

Laurenz Albe <laurenz.albe@xxxxxxxxxxx> · Fri, 28 Aug 2020 13:40:43 +0200

On Thu, 2020-08-27 at 12:55 -0300, Fontana Daniel C (Desartec S.R.L.) 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?

You have several options:

1. Repeat the literal:

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

2. Use a subquery:

  select ls_number,
         substr (ls_number, 3, 3)
  FROM (SELECT '1234567890' AS ls_number) AS q;

3. Use a CTE:

  WITH x AS (SELECT '1234567890' as ls_number)
  SELECT ls_number,
         substr (ls_number, 3, 3)
  FROM x;

Yours,
Laurenz Albe
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