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Hive, mail # user - Enhancing Query Join to speed up Query


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Re: Enhancing Query Join to speed up Query
Stephen Sprague 2013-06-13, 17:42
Hi naja,
test those two versions (or three now) and report back to the group.  :)
even if some smarty-pants thinks he knows the answer its always good to
confirm things are as they should be.
On Wed, Jun 12, 2013 at 11:54 PM, Sanjay Subramanian <
[EMAIL PROTECTED]> wrote:

>  Hi
>
>  I would actually do it like this…so that the set on the left of JOIN
> becomes smaller
>
>  SELECT a.item_id, a.create_dt
> FROM
>      ( SELECT
>                     item_id, create_dt
>       FROM
>                     A
>       WHERE
>                    item_id = 'I001'
>        AND
>                   category_name = 'C001'
>       )  a
> JOIN
>          b
> ON
>         a.item_id = b.item_id
> ;
>
>
>   From: Naga Vijay <[EMAIL PROTECTED]>
> Reply-To: "[EMAIL PROTECTED]" <[EMAIL PROTECTED]>
> Date: Wednesday, June 12, 2013 9:17 PM
> To: "[EMAIL PROTECTED]" <[EMAIL PROTECTED]>
> Subject: Enhancing Query Join to speed up Query
>
>    Hi,
>
> Which of the two query options is better?
>
> SELECT a.item_id, a.create_dt
> FROM   a JOIN b
> ON     (a.item_id = b.item_id)
> WHERE  a.item_id = 'I001'
> AND    a.category_name = 'C001';
>
>  - or -
>
> SELECT a.item_id, a.create_dt
> FROM   a JOIN b
> ON     (a.item_id = b.item_id AND a.item_id = 'I001')
> WHERE  a.category_name = 'C001';
>
>  Thanks
>  Naga
>
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