From: Bruno Wolff III <bruno@wolff.to>
To: pgsql-sql@postgresql.org
Subject: Using union to avoid creating temp table
Date: Mon, 1 Jul 2002 11:31:40 -0500
Message-ID: <20020701163140.GA22475@wolff.to> (raw)
I don't know if this is a well known trick or not. I wanted to check a
list of values inputted to a script against some existing tables. I was
trying to think of alternatives to using a temp table and copy since
this would take two requests instead of one.
What I ended up doing is building the input values into sepearte
select statements unioned together. So if the input values were
'abc', 'def' and 'ghi', I would end up doing a select like:
select add.id from (select 'abc' union select 'def' union select 'ghi') add (id)where not exists (select from role where add.id = role.id)
I don't know whether or not this is faster in general, but it probably is
under at least some circumstances.
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To: pgsql-sql@postgresql.org
Cc: bruno@wolff.to
Subject: Re: Using union to avoid creating temp table
In-Reply-To: <20020701163140.GA22475@wolff.to>
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