From: Bruno Wolff III <bruno@wolff.to>
To: chester c young <chestercyoung@yahoo.com>
Cc: pgsql-sql@postgresql.org
Subject: Re: outer join versus not exists
Date: Tue, 18 Mar 2003 11:30:55 -0600
Message-ID: <20030318173055.GA21021@wolff.to> (raw)
In-Reply-To: <20030318165427.52097.qmail@web12703.mail.yahoo.com>
References: <20030318165427.52097.qmail@web12703.mail.yahoo.com>
On Tue, Mar 18, 2003 at 08:54:27 -0800,
chester c young <chestercyoung@yahoo.com> wrote:
> In pg, is there any performance gain in using outer join with null as
> versus using not exists, eg:
>
> select t1.* from t1 right join t2 using( id ) where t2.id is null;
>
> versus
>
> select * from t1 where not exists (select 1 from t2 where t1.id=t2.id);
You can use explain analyze to compare the queries.
Another possible approach is:
select t1.* from t1, (select id from t1 except select id from t2) t3
where t1.id = t3.id;
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To: pgsql-sql@postgresql.org
Cc: bruno@wolff.to, chestercyoung@yahoo.com
Subject: Re: outer join versus not exists
In-Reply-To: <20030318173055.GA21021@wolff.to>
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