RE: sql comparison between records

I need to calculate the average duration between records for records that
can be grouped by key.  The real world application is mean time between
clicks in a web site session.  Regardless, it's kind of interesting in the
abstract, IMHO.  I was a big fan of Joe Celko's column when it used to
appear in a now defunct freebie trade magazine.  One of the recurring
implicit themes of his column was the difference between the types of
problems that were naturally suited to a procedural language and those that
were better suited to SQL.  

> -----Original Message-----
> From: thomas@inorbit.com [mailto:thomas@inorbit.com]
> Sent: Tuesday, July 24, 2001 8:01 PM
> To: MIDRANGE-L@midrange.com
> Subject: Re: sql comparison between records
> 
> 
> Joel:
> 
> Since SQL is designed to handle sets of records, individual 
> record operations often aren't appropriate for it. But can 
> you clarify whether you actually need specific durations 
> between records or you want to use those durations only to 
> end up with an eventual average and the individual durations 
> will then be discarded? The second alternative might be 
> reasonably possible with SQL.
> 
> Tom Liotta
> 
> On Fri, 20 July 2001, Joel Fritz wrote:
> 
> > 
> > How do you do this in SQL?
> > 
> > I have a file ordered by key value and a timestamp.  There 
> are multiple
> > records for each key value. I want to find the difference 
> between time
> > stamps of successive records and calculate the average 
> difference for a key
> > value group.  I know, it's easy in RPG.  I'm not trying to measure
> > programmer productivity. <g>
> 
> -- 
> Tom Liotta
> The PowerTech Group, Inc.
> 19426 68th Avenue South
> Kent, WA 98032
> Phone  253-872-7788
> Fax  253-872-7904
> http://www.400Security.com
> 
> 
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