Re: JOIN a table twice for different values in the same query

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От Phillip Smith
Тема Re: JOIN a table twice for different values in the same query
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Msg-id 002f01c853d7$63bc0680$9b0014ac@wbaus090
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Ответ на JOIN a table twice for different values in the same query  (Colin Wetherbee <cww@denterprises.org>)
Ответы Re: JOIN a table twice for different values in the same query  (Colin Wetherbee <cww@denterprises.org>)
Список pgsql-sql
Try something like this where we alias the joined tables:

SELECT departure_date, j1.code AS departure_code, j2.code AS arrival_code
FROM jsjourneys
LEFT OUTER JOIN jsports AS j1 ON jsjourneys.departure_port = j1.id
LEFT OUTER JOIN jsports AS j2 ON jsjourneys.arrival_port = j2.id;

As a side note - all the IATA codes are unique for each airport - wouldn't
it be better to use these as the Primary Key and Foreign Keys? Then you
wouldn't have to even join the tables unless you wanted the port names (not
just the code)

Cheers,
~p


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