Re: Why is this a cross join?
От | Tim Uckun |
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Тема | Re: Why is this a cross join? |
Дата | |
Msg-id | CAGuHJrMD6inC5mqiGg1Jh2R7dBJbM6rqW+q3UeYHNi68+oT6ng@mail.gmail.com обсуждение исходный текст |
Ответ на | Re: Why is this a cross join? (Tony Theodore <tony.theodore@gmail.com>) |
Ответы |
Re: Why is this a cross join?
Re: Why is this a cross join? Re: Why is this a cross join? Re: Why is this a cross join? |
Список | pgsql-general |
> > In some way, every join is a cross join, with the results filtered according to the specificity of the join conditions.In this case: > > inner join model_configurations mc on left(crm.customer_class, 6) = left(mc.sap_code,6) > > "customer_class" sounds like a fairly generic sort of field, so you'd expect many matches. Truncating the fields is likelyto make this even less specific, returning more results. > I guess I am not explaining it properly.. Say I created new columns on both tables called "first_6" and populated them with the substrings. If I did a inner join or a left join on those fields would I still get a cross join? inner join model_configurations mc on mc.first_6 = crm.first_6
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