Re: Most efficient way of querying M 'related' tables where N out of M may contain the key

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От David G. Johnston
Тема Re: Most efficient way of querying M 'related' tables where N out of M may contain the key
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Msg-id CAKFQuwY=xA3q4RuGwC5hFDUtQmquXWtXrtLR0ymsDk2POitUCA@mail.gmail.com
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Ответ на Most efficient way of querying M 'related' tables where N out of M may contain the key  (Stephane Bailliez <sbailliez@gmail.com>)
Ответы Re: Most efficient way of querying M 'related' tables where N out of M may contain the key  (Stephane Bailliez <sbailliez@gmail.com>)
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On Thu, Aug 20, 2015 at 8:03 PM, Stephane Bailliez <sbailliez@gmail.com> wrote:
Pretty bad subject description... but let me try to explain. 


I'm trying to figure out what would be the most efficient way to query data from multiple tables using a foreign key.


​SELECT [...]
FROM (SELECT reference_id, [...] FROM table_where_referenced_id_is_a_pk WHERE reference_id EXISTS/IN/JOIN)​
 
​src
​LEFT JOIN type1 USING (reference_id)
LEFT JOIN type2 USING (reference_id)
[...]

Or consider whether PostgreSQL Inheritance would work - though basically its a friendly API over the "UNION ALL" query you proposed.

David J.

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