On 30 June 2011 22:59, Chris Campbell <ccampbell@cascadeds.com> wrote:
> Using PostgreSQL 9.0.2 I’m trying to write a sql statement to extract
> specific rows from the following data set. I’ve looked at the documentation
> that talks about the Max() function but the example doesn’t go far enough:
>
> The sample fields/dataset are as follows
>
> PaymentKey, ContactKey, PaymentDate
> 1, 100, 01/01/2011
> 2, 100, 12/30/2010
> 3, 100, 12/31/2010
> 4, 101, 01/02/2011
> 5, 101, 12/25/2010
>
> What I want returned are rows grouped by contactkey showing the
> corresponding payment key and payment date for the record that has the max
> (newest) payment date. So I would want my result set to look like this:
>
> 1, 100, 01/01/2011
> 4, 101, 01/02/2011
>
> I would be using this query as a sub query that is (left) joined to a master
> query by ContactKey
It should look something like this:
SELECT contactkey, max(paymentdate)
FROM my_table
GROUP BY contactkey;
You'll need to adapt it for your joined query as I don't know what
your join looks like.
Regards
Thom Brown
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