| From: | Tim Landscheidt <tim(at)tim-landscheidt(dot)de> |
|---|---|
| To: | pgsql-sql(at)postgresql(dot)org |
| Subject: | Re: complex join question |
| Date: | 2010-02-12 23:55:38 |
| Message-ID: | m3vde2ko05.fsf@passepartout.tim-landscheidt.de |
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| Lists: | pgsql-sql |
Louis-David Mitterrand <vindex+lists-pgsql-sql(at)apartia(dot)org> wrote:
> Here is my schema:
> cruise_line -> ship(id_line) -> cruise_type(id_ship) -> cruise(id_cruise_type)
> -> price(id_cruise, id_currency) <- currency (USD,GBP,EUR,CAD)
> (a 'cruise' is a 'cruise_type' + a date)
> I am trying to display a count of cruise's for each ship and each
> currency even if that count is 0.
> But I am having trouble building the query, as some 'cruise's might not
> (yet) have a 'price' in all currencies and so no link to 'currency'.
You're probably looking for a "LEFT JOIN".
Tim
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