From: | Richard Huxton <dev(at)archonet(dot)com> |
---|---|
To: | Havasvölgyi Ottó <h(dot)otto(at)freemail(dot)hu> |
Cc: | pgsql-general(at)postgresql(dot)org |
Subject: | Re: field alias in where condition |
Date: | 2005-06-03 14:53:55 |
Message-ID: | 42A06F03.3080306@archonet.com |
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Thread: | |
Lists: | pgsql-general |
Havasvölgyi Ottó wrote:
> Hi all,
>
> I issued the following queries:
>
>
> select substring(proname from 1 to 1) as nevresz, count(*)
> from pg_proc
> where nevresz = 'a'
> order by nevresz
> group by nevresz;
>
> select substring(proname from 1 to 1) as nevresz, count(*)
> from pg_proc
> order by nevresz
> group by nevresz;
>
> The first query fails, and says that column 'nevresz' does not exist.
> The second is OK.
>
> What is the problem? I cannot use column alias in where condition?
Correct. SQL defines it that way. You could reformulate as a sub-query
if you wanted:
SELECT nevresz,count(*)
FROM
(
SELECT substring(proname from 1 to 1) as nevresz FROM pg_proc
) AS dummy
GROUP BY nevresz
ORDER BY nevresz
--
Richard Huxton
Archonet Ltd
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