Re: Outer join with where conditions

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От Bruno Wolff III
Тема Re: Outer join with where conditions
Дата
Msg-id 20051114162920.GA27026@wolff.to
обсуждение исходный текст
Ответ на Outer join with where conditions  (Michał Otroszczenko <michal.otroszczenko@gmail.com>)
Список pgsql-general
On Mon, Nov 14, 2005 at 14:45:22 +0100,
  Michał Otroszczenko <michal.otroszczenko@gmail.com> wrote:
> Hello,
>
> I wonder If I could move additional join condition from ON part of
> query to where part.

Yes, but the semantics are different for outer joins.

>
> For example instead of:
>
> SELECT *  FROM
>     booking_load AS bload
>     LEFT OUTER JOIN dict_load_type_tsl AS load_tsl ON (
>                     load_tsl.dict_load_type_id = bload.dict_load_type_id
>                     AND load_tsl.dict_language_id = 'EN' ))
>
> Could I write:
>
> SELECT *  FROM
>     booking_load AS bload
>     LEFT OUTER JOIN dict_load_type_tsl AS load_tsl USING (dict_load_type_id)
> WHERE
>      load_tsl.dict_language_id = 'EN'
>
> I thought that second query could be more 'optimizable', but gave no results.
> Where is the problem ?
>
> Best regards,
> Michal
>
> ---------------------------(end of broadcast)---------------------------
> TIP 6: explain analyze is your friend

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