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Re: SQL query question

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: alloni(at)aposiopesis(dot)net
Cc: pgsql-novice(at)postgresql(dot)org
Subject: Re: SQL query question
Date: 2005-08-15 00:31:02
Message-ID: (view raw, whole thread or download thread mbox)
Lists: pgsql-novice
"Alloni Kramer" <alloni(at)aposiopesis(dot)net> writes:
> Simplified version of problem:  We have a table.  We'll say it has four
> variables, a, b, c, and squelch, all ints.  I want to get all values of
> these variables for which:

> c is within a certain range of values (call it between 3 and 5).
> for any given value of a, c is maximum.
>  - and -
> for any given value of a for which c is maximal, b is maximum.  That is,
> if we have the values of

This isn't perfectly clear, but I think what you are after can be done

	select distinct on (a) * from mytab
	where c between 3 and 5
	order by a, c desc, b desc;

The "weather report" example in the SELECT reference page may be

It's possible to do this without the nonstandard DISTINCT ON clause,
but it's a lot more tedious (and I forget just how at the moment ;-))

			regards, tom lane

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