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From: Amos Hayes <ahayes@polkaroo.net>
Subject: Re: Find min and max values across two columns?
Date: Fri, 24 Mar 2006 16:34:43 -0500
To: Rod Taylor <pg@rbt.ca>, Tom Lane <tgl@sss.pgh.pa.us>


Your tips were great and I have hunted down the relevant pages in the  
docs. Thanks guys!

--
Amos

On 24-Mar-06, at 4:20 PM, Rod Taylor wrote:

> On Fri, 2006-03-24 at 16:20 -0500, Tom Lane wrote:
>> 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.
>
> Thanks. I could not remember one way or the other.
>
> -- 
>
>
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