Re: Getting all rows even if not a member of any groups
От | Bruno Wolff III |
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Тема | Re: Getting all rows even if not a member of any groups |
Дата | |
Msg-id | 20030627151025.GE15269@wolff.to обсуждение исходный текст |
Ответ на | Re: Getting all rows even if not a member of any groups (Együd Csaba <csegyud@freemail.hu>) |
Список | pgsql-sql |
On Fri, Jun 27, 2003 at 16:18:10 +0200, Együd Csaba <csegyud@freemail.hu> wrote: > > This is absolutelly what I want, but I can't understand how it is working. > Where can I find a descriptive (tale-like, for kids ... :) ) documentation > about using joins? If you look at the documentation for the select command and page down a bit there is a description of join syntax. Note that in 7.4 using the explicit join syntax won't force join order. (This really only affects cross joins and inner joins; left and right joins normally can't be reordered.) You need a left join to pick up products that aren't in any group. The parenthesis changed the join order so that group names were attached to group ids before group ids were joined to products. This can have performance implications. I think that this is probably the faster way, but the other option would to have been to make the second join a left join as well.
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