From: Tom Lane <tgl@sss.pgh.pa.us>
To: Rod Taylor <pg@rbt.ca>
Cc: Amos Hayes <ahayes@polkaroo.net>
Cc: pgsql-sql@postgresql.org
Subject: Re: Find min and max values across two columns?
Date: Fri, 24 Mar 2006 16:20:31 -0500
Message-ID: <10495.1143235231@sss.pgh.pa.us> (raw)
In-Reply-To: <1143233215.90799.91.camel@home>
References: <DAD4674C-1896-4F24-B43B-B884491DB931@polkaroo.net>
<1143233215.90799.91.camel@home>
Rod Taylor <pg@rbt.ca> writes:
> The reason for the subselect is to prevent multiple calculations of
> individual column aggregates. I believe it *may* be calculated multiple
> times otherwise this would work just as well:
> select case when max(a) > max(b) then max(a) else max(b) end as max from
> tab;
Just for the record, we've gotten that right since 7.4. greatest()
would be a notationally cleaner solution than CASE, but multiple
occurrences of identical aggregates don't cost much of anything.
regards, tom lane
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To: pgsql-sql@postgresql.org
Cc: tgl@sss.pgh.pa.us, pg@rbt.ca, ahayes@polkaroo.net
Subject: Re: Find min and max values across two columns?
In-Reply-To: <10495.1143235231@sss.pgh.pa.us>
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