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Date: Sun, 18 Mar 2007 18:21:54 -0700 (PDT)
From: chester c young <chestercyoung@yahoo.com>
Subject: better approach: case or join
To: sql pgsql <pgsql-sql@postgresql.org>
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Message-ID: <828472.77350.qm@web54308.mail.yahoo.com>

from id extracting name from several tables.  which is generally the
better approach?

select case when tab_tla='usr' then (select name from users where ... )
       case when tab_tla='con' then (select title from contents where
...)
end    as name;

as versus

select  name
from    users
where   tab_tla='usr' and ...
        join
select  title
from    contents
where   tab_tla='con' and ...

I assume the former since the optimizer does not examine whether the
entire where clause might be false before executing the query.

thanks,
chester


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