From: | Stephan Szabo <sszabo(at)megazone23(dot)bigpanda(dot)com> |
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To: | Don Baccus <dhogaza(at)pacifier(dot)com> |
Cc: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Hackers List <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: Functions returning sets |
Date: | 2001-05-20 18:55:02 |
Message-ID: | Pine.BSF.4.21.0105201144170.54047-100000@megazone23.bigpanda.com |
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Lists: | pgsql-hackers |
On Sun, 20 May 2001, Don Baccus wrote:
> At 10:55 AM 5/20/01 -0700, Stephan Szabo wrote:
> > Can the IN always get written as a
> >join and is it always better to do so?
>
> Nope:
> ...
> A better question, I guess, is if it is always better to write
> it as a join if the left hand operand is a table column and
> the right hand operand a rowset.
Well I was assuming we were talking about the subquery case
in general :)
It might be a problem with subqueries with set value functions
and parameters passed down from the outer tables:
select * from blah where
blah.val1 in
(select count(*) from blah2 where blah2.val2=blah.val2
group by blah2.val3);
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