From: Richard Huxton <dev@archonet.com>
To: "Philippe Lang" <philippe.lang@attiksystem.ch>, <pgsql-sql@postgresql.org>
Subject: Re: sub-select parameter problem
Date: Thu, 4 Mar 2004 11:51:21 +0000
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On Thursday 04 March 2004 11:20, Philippe Lang wrote:
[working query]

> It works fine.

Excellent! :-)
Oh - there's more :-(

> Now, I need to do something else: the parameter of my sub-select is also
> a member of the table I'm selecting.
>
> SELECT
>
>   tableA.field1,
>   tableA.field2,
>
>   tableB.field1,
>   tableB.field2,
>
>   (
>     SELECT tableB.field2
>     FROM tableB
>     WHERE tableB.field1 = tableB.field1 (--> from-main-select?) - 1;
>   ) AS p
>
> FROM tableA
> INNER JOIN tableB
> ON tableA.pk = tableB.FK;
> -------------------------------------------
>
> How can I refer to the tableB.field1 parameter from the main query? I've
> tried to do something like this, but without success:

You're along the right lines, except I think you want to alias the table not 
the column.

...
(
  SELECT x.field2
  FROM tableB AS x
  WHERE x.field1 = tableB.field1 - 1
)
...

HTH
-- 
  Richard Huxton
  Archonet Ltd