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