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Re: Combining two queries - Mailing list pgsql-general

From Robert DiFalco
Subject Re: Combining two queries
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Msg-id CAAXGW-zsAyN9PEtoEojXgvqUWS+WWsGcaWmO0oDVv07KW2dffw@mail.gmail.com
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In response to Re: Combining two queries  (David G Johnston <david.g.johnston@gmail.com>)
Responses Re: Combining two queries
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Is the intersect any better than what I originally showed? On the ROW approach, I'm not sure where the context for that is coming from since it may not be in the intersection. Consider n1 and n2 are NOT friends but they have >0 mutual friends between them.

On Thu, Dec 18, 2014 at 1:29 PM, David G Johnston <david.g.johnston@gmail.com> wrote:
Robert DiFalco wrote
> For 2 arbitrary ids, I need a query to get two pieced of data:
>    * Are the two users friends?

This seems easy...ROW(u_id, f_id) = ROW(n1, n2)


>    * How many friends do the two users have in common.

SELECT f_id FROM [...] WHERE u_id = n1
INTERSECT
SELECT f_id FROM [...] WHERE u_id = n2

Put those into WITH/CTE and use the main query to combine them in whatever
way seems appropriate.

David J.




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