Re: Union instead of Outer Join

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От Jeff Eckermann
Тема Re: Union instead of Outer Join
Дата
Msg-id 20020117200103.3742.qmail@web20802.mail.yahoo.com
обсуждение исходный текст
Ответ на Union instead of Outer Join  ("Unnikrishnan Menon" <unnikrishnan.menon@chennai.transys.net>)
Список pgsql-sql
select   item_code, coalesce(user_id, ' ') as user_id
from   item_list l inner join user_detail s on l.user_id
= s.user_id   left outer join  user_detail b on l.other_userid =
b.user_id
where   l.item_code = 1234;

Joins can be named in different ways; see the "SELECT"
page in the "SQL Commands" section of the docs.

Your message suggests that you want a right join on b
& l; the syntax above corresponds to what you stated
(per my Oracle reference).

--- Unnikrishnan Menon
<unnikrishnan.menon@chennai.transys.net> wrote:
> Hi,
> 
> I have this query in oracle which I'am trying to
> port to PostgreSQL :
> 
> Select 
>     item_code, nvl(user_id,' ') as user_id 
> from 
>     item_list L, User_detail B, User_detail S
> where 
>     L.user_id = S.User_id and
>     L.other_userid = B.user_id(+) and
>     L.item_code = 1234;
> 
> This query gives me 1 row as result. L.other_userid
> could be null.
> 
> I try changing the query thus in postgreSQL :
> 
> Select 
>     item_code, nvl(user_id,' ') as user_id 
> from 
>     item_list L, User_detail B, User_detail S
> where 
>     L.user_id = S.User_id and
>     L.other_userid = B.user_id and
>     L.item_code = 1234
> Union
> Select 
>     item_code, nvl(user_id,' ') as user_id 
> from 
>     item_list L, User_detail B, User_detail S
> where 
>     L.user_id = S.User_id and
>     L.item_code = 1234 and
>     0 = ( Select 
>                  count(*) 
>             from 
>                  listed_items L, user_detail B,
> user_detail S
>             where 
>                 L.other_userid = B.user_id);
> 
> The above query does not return any row. Where could
> I be going wrong?
> 
> Any help would be appreciated.
> 
> Thanx in advance
> 
> Unni
> 


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