Re: JOIN a table twice for different values in the same query
От | Colin Wetherbee |
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Тема | Re: JOIN a table twice for different values in the same query |
Дата | |
Msg-id | 47869EF7.70106@denterprises.org обсуждение исходный текст |
Ответ на | Re: 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
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Список | pgsql-sql |
Colin Wetherbee wrote: > Phillip Smith wrote: >> 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) > > This is true, but FWIW, my application will mostly be joining for the > name of the airport or the city, not the code. > > I'll keep the idea of using the codes as keys in mind, though. Thanks > for pointing that out. Oh, now I remember why I'm using IDs as keys. ;) The code isn't always going to be an airport, and, for example, a train station in Buenos Aires could conceivably have the same code as a shipping port in Rotterdam, which, in turn, might well be JFK. :) Colin
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