Обсуждение: EXTERN JOIN with WHEN query

Hi all;
This is a query that I guess is not very difficult, but I'm a newbie;
I've got a lot of tables, each of them with two columns:

SELECT * FROM precal; ->
  (date)     (real)
   fecha    | precipitacion
------------+---------------
 1996-01-01 |             0.6
 1996-02-01 |             0.7
...


But in this table there are some inexistents records (some missing days)
And I would like to create lists with a full list of dates and corresponding
precipitation data, with gaps when the row didn't exist.
So; I've created a table with a complete series of dates from 1950 up to
date, and made the query:

 SELECT fechas.fecha,precipitacion FROM fechas LEFT OUTER JOIN precal41 ON
(fechas.fecha  = precal41.fecha);

This is perfect. But to make it better,  would like to include just the dates
from the first one in the precal table. So, I've tried:

SELECT fechas.fecha,precipitacion FROM fechas LEFT OUTER JOIN precal41 ON
(fechas.fecha  = precal41.fecha) WHEN fechas.fecha >= min(precal41.fecha);

With the answer:

ERROR:  parser: parse error at or near "WHEN"

Could you help me with this query?

Thanks and regards

Javier

-------------------------------------------------------

On Thu, Jun 05, 2003 at 16:56:54 +0200,
  javier garcia - CEBAS <rn001@cebas.csic.es> wrote:
>
> SELECT fechas.fecha,precipitacion FROM fechas LEFT OUTER JOIN precal41 ON
> (fechas.fecha  = precal41.fecha) WHEN fechas.fecha >= min(precal41.fecha);
>
> With the answer:
>
> ERROR:  parser: parse error at or near "WHEN"
>
> Could you help me with this query?

The keyword should be "WHERE" instead of "WHEN".

On Thursday 05 Jun 2003 3:56 pm, javier garcia - CEBAS wrote:
> But in this table there are some inexistents records (some missing days)
> And I would like to create lists with a full list of dates and
> corresponding precipitation data, with gaps when the row didn't exist.
> So; I've created a table with a complete series of dates from 1950 up to
> date, and made the query:
>
>  SELECT fechas.fecha,precipitacion FROM fechas LEFT OUTER JOIN precal41 ON
> (fechas.fecha  = precal41.fecha);
>
> This is perfect. But to make it better,  would like to include just the
> dates from the first one in the precal table. So, I've tried:
>
> SELECT fechas.fecha,precipitacion FROM fechas LEFT OUTER JOIN precal41 ON
> (fechas.fecha  = precal41.fecha) WHEN fechas.fecha >= min(precal41.fecha);

Perhaps something like (not tested):

SELECT .... WHERE fechas.fecha >= (SELECT min(precal41.fecha) FROM precal41);
--
  Richard Huxton

On Thu, 5 Jun 2003 16:56:54 +0200, javier garcia - CEBAS
<rn001@cebas.csic.es> wrote:
>SELECT fechas.fecha,precipitacion FROM fechas LEFT OUTER JOIN precal41 ON
>(fechas.fecha  = precal41.fecha) WHEN fechas.fecha >= min(precal41.fecha);
>
>With the answer:
>
>ERROR:  parser: parse error at or near "WHEN"

The keyword is "WHERE".  And I guess the WHERE clause has to be

    WHERE fechas.fecha >= (SELECT min(fecha) FROM precal41)

or, if there is an index on precal41.fecha, more efficiently but
non-standard

    WHERE fechas.fecha >= (SELECT fecha
                             FROM precal41 ORDER BY fecha LIMIT 1)

HTH.
Servus
 Manfred

Subject: Re: [GENERAL] EXTERN JOIN with WHEN query
Date: Friday 06 June 2003 10:57
From: Darko Prenosil <darko.prenosil@finteh.hr>
To: javier garcia - CEBAS <rn001@cebas.csic.es>

On Thursday 05 June 2003 16:56, javier garcia - CEBAS wrote:
> Hi all;
> This is a query that I guess is not very difficult, but I'm a newbie;
> I've got a lot of tables, each of them with two columns:
>
> SELECT * FROM precal; ->
>   (date)     (real)
>    fecha    | precipitacion
> ------------+---------------
>  1996-01-01 |             0.6
>  1996-02-01 |             0.7
> ...
>
>
> But in this table there are some inexistents records (some missing days)
> And I would like to create lists with a full list of dates and
> corresponding precipitation data, with gaps when the row didn't exist.
> So; I've created a table with a complete series of dates from 1950 up to
> date, and made the query:
>
>  SELECT fechas.fecha,precipitacion FROM fechas LEFT OUTER JOIN precal41 ON
> (fechas.fecha  = precal41.fecha);
>
> This is perfect. But to make it better,  would like to include just the
> dates from the first one in the precal table. So, I've tried:
>
> SELECT fechas.fecha,precipitacion FROM fechas LEFT OUTER JOIN precal41 ON
> (fechas.fecha  = precal41.fecha) WHEN fechas.fecha >= min(precal41.fecha);
>
> With the answer:
>
> ERROR:  parser: parse error at or near "WHEN"
>
> Could you help me with this query?

Maybe WHERE instead of WHEN ?

-------------------------------------------------------

On Thu, 5 Jun 2003, javier garcia - CEBAS wrote:

> Hi all;
> This is a query that I guess is not very difficult, but I'm a newbie;
> I've got a lot of tables, each of them with two columns:
>
> SELECT * FROM precal; ->
>   (date)     (real)
>    fecha    | precipitacion
> ------------+---------------
>  1996-01-01 |             0.6
>  1996-02-01 |             0.7
> ...
>
>
> But in this table there are some inexistents records (some missing days)
> And I would like to create lists with a full list of dates and corresponding
> precipitation data, with gaps when the row didn't exist.
> So; I've created a table with a complete series of dates from 1950 up to
> date, and made the query:

Any time you're gonna do this, you can make a table with all the dates in
it already, and left join against that.

I.e. if you want a report for every month, numbered 1 through 12, then
just create a table with an id 1 to 12 and the names of the months.  Since
the table's so small, it doesn't even really need indexes.