Re: Need sql to pull data from terribly architected table

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От David Johnston
Тема Re: Need sql to pull data from terribly architected table
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Msg-id 017d01cdb156$399a9bf0$accfd3d0$@yahoo.com
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Ответ на Re: Need sql to pull data from terribly architected table  ("Gauthier, Dave" <dave.gauthier@intel.com>)
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From: pgsql-general-owner@postgresql.org [mailto:pgsql-general-owner@postgresql.org] On Behalf Of Gauthier, Dave
Sent: Tuesday, October 23, 2012 3:31 PM
To: pgsql-general@postgresql.org
Subject: Re: [GENERAL] Need sql to pull data from terribly architected table

 

Thanks for the answers.  But I also have a predicate...

 

select col1,col2 from foo where col4='c4' and col5 <> 'xxx';

 

How is that done?

 

From: Richard Broersma [mailto:richard.broersma@gmail.com]
Sent: Tuesday, October 23, 2012 3:24 PM
To: chris@chriscurvey.com
Cc: Gauthier, Dave; pgsql-general@postgresql.org
Subject: Re: [GENERAL] Need sql to pull data from terribly architected table

 

 

On Tue, Oct 23, 2012 at 12:21 PM, Richard Broersma <richard.broersma@gmail.com> wrote:

On Tue, Oct 23, 2012 at 12:06 PM, Chris Curvey <chris@chriscurvey.com> wrote:

select my_ids.id 

, c1.value as col1

, c2.value as col2

, c3.value as col3

, c4.value as col4

, c5.value as col5

from my_ids

left join foo c1 on my_ids.id = c1.id

left join foo c2 on my_ids.id = c2.id

left join foo c3 on my_ids.id = c3.id

left join foo c4 on my_ids.id = c4.id

left join foo c5 on my_ids.id = c5.id


How about:

oops - I had some malformed air code
 

SELECT my_ids.id, ARRAY_AGG( ( property, value ) order by (property, value) )
  FROM my_ids

   GROUP BY id

ORDER BY id;


--
Regards,
Richard Broersma Jr.




--
Regards,
Richard Broersma Jr.

 

 

You put the above query into a sub-select or CTE (WITH) and then in the outer query you apply whatever where clause you want.

 

If you want to try and help the planner you could do:

 

SELECT some_id FROM foo WHERE property = ‘…’ AND value = ‘…’

UNION ALL

SELECT some_id FROM foo WHERE property = ‘…’ AND value = ‘…’

 

To pre-define which IDs are candidates and then use that information later on in the query.

 

Whether this is a worthwhile effort I have no idea and it may not matter anyway depending on how well the brute-force approach works given your data.

 

David J.

 

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