From: | Louis-David Mitterrand <vindex+lists-pgsql-sql(at)apartia(dot)org> |
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To: | pgsql-sql(at)postgresql(dot)org |
Subject: | Re: UNION or LEFT JOIN? |
Date: | 2010-02-16 21:02:23 |
Message-ID: | 20100216210222.GA20610@apartia.fr |
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Lists: | pgsql-sql |
On Tue, Feb 16, 2010 at 03:33:23PM +0000, Oliveiros wrote:
> Louis-David,
>
> Please advice me,
Hi Oliveiros,
> if some cabin doesn't have a price i.e. it is not available, is there some
> way to tell
> which cruise it belongs to?
In fact a cabin belongs to a ship and CAN be associated to a 'cruise'
event with a price(id_cruise,id_cabin) object.
> You have PRICE table which seems to me to be an associative table between
> cruise and cabin, is this correct?
Yes,
> But, if the price doesn't have a register for that pair
> (îd_cabin,id_cruise), how do you know that cabin belongs to that cruise, in
> this case, cruise nº 1?
I am trying to display a list of all cabins of a ship for a certain
cruise even if some prices are missing, so the user sees what cabins are
not available.
After much trial and error I was finally able to build a left join query
that works.
Thanks a lot for offering your help!
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