Re: Problem with phone list.

--- Mike Diehl <jdiehl@sandia.gov> wrote:

> I've qot a problem I need to solve.  I'm sure it's pretty simple; I just can't 
> seem to get it, so here goes...
> 
> I've got a table, actually a view that joins 3 tables, that contains a phone 
> number, a unique id, and a call duration.
> 
> The phone number has duplicates in it but the unique id is unique.
> 
> I need to get a list of distinct phone numbers and the coorisponding largest 
> call duration.
> 
> I've got the idea that this should be a self-join on phone number where 
> a.id<>b.id, but I just can't seem to get the max duration.
 SELECT phone_number, max( duration ) as max_duration   FROM your_view
GROUP BY phone_number;

if you need the unique Id also,
 SELECT DISTINCT ON ( phone_number ) id, phone_number, duration   FROM your_view
ORDER BY duration desc;

or   SELECT V1.id, V1.phone_number, V1.duration     FROM your_view AS V1
INNER JOIN ( SELECT phone_number, max( duration )              FROM your_view          GROUP BY phone_number ) AS V2(
phone_number,duration )       ON (V1.phone_number, V1.duration) = (V2.phone_number, V2.duration);
 

Regards,
Richard Broersma Jr.