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 From: Mike Yearwood
  Where is Mike Yearwood?
 Toronto
 Canada
 Mike Yearwood
 To: Ellen Solomon
  Where is Ellen Solomon?
 Bet Shemesh
 Israel
 Ellen Solomon
 Tags
Subject: RE: count records of closed table?
Thread ID: 155321 Message ID: 155352 # Views: 1 # Ratings: 1
Version: Visual FoxPro 9 Category: General VFP Topics
Date: Monday, December 31, 2007 4:34:49 AM         
   


> >
> > Ellen
> >
> > Your query will give you the result but does not feel optimised. In case you expect the interval to be large, it may be faster to add 1 record at a time to the cursor.
> >
> > Regards
> > Tushar
>
>
> Hi Tushar.
>
> Considering the cursor is an attempt at efficiency, I'd love to make it more efficient!
>
> The concern is to take records from throughout the table, otherwise the sampling might not be broad enough. (1/3 top, 1/3 middle, 1/3 end definitely wouldn't cut it.) The table does not have an ID, nor is it indexed - I'm not sure whether doing either is worthwhile just to create a sample.
>
> (Although come to think of it we take 4 different samples, which occur at different phases of processing and for different sample sizes; perhaps two of them can share a cursor but not all 4.)
>
> Any suggestions? What other information can I give about the data? (I didn't understand your suggestion about adding one record at a time - how to implement that.)
>

This is a technique I used long long ago. We called it FIRS - Fixed Interval Random Start.

use sourcetable
set order to sometag
rand(-1)
rs = int(rand()*100)+1
fi = reccount()/100
go m.rs
do while not eof()
insert into samplecursor (fieldnames...) values (fields from sourcetable)
skip m.fi
enddo

HTH

Mike Yearwood
www.foxridgesoftware.com
President: Toronto Ontario FoxPro User's Group

ENTIRE THREAD

count records of closed table? Posted by Ellen Solomon @ 12/29/2007 10:38:26 PM
RE: count records of closed table? Posted by Eric den Doop @ 12/29/2007 10:50:53 PM
RE: count records of closed table? Posted by Ellen Solomon @ 12/29/2007 11:39:47 PM
RE: count records of closed table? Posted by Koen Piller @ 12/30/2007 10:24:22 AM
RE: count records of closed table? Posted by Ellen Solomon @ 12/30/2007 10:32:35 AM
RE: count records of closed table? Posted by Koen Piller @ 12/30/2007 2:31:03 PM
RE: count records of closed table? Posted by tushar @ 12/30/2007 6:34:41 PM
RE: count records of closed table? Posted by Ellen Solomon @ 12/30/2007 8:55:08 PM
RE: count records of closed table? Posted by tushar @ 12/31/2007 4:30:32 AM
RE: count records of closed table? Posted by Mike Yearwood @ 12/31/2007 4:34:49 AM
RE: count records of closed table? Posted by Ellen Solomon @ 12/31/2007 10:43:53 AM
RE: count records of closed table? Posted by Hugo Ranea @ 12/31/2007 6:17:26 PM
RE: count records of closed table? Posted by Tamar Granor @ 1/3/2008 10:45:33 PM
RE: count records of closed table? Posted by Ellen Solomon @ 1/5/2008 5:04:13 PM
RE: count records of closed table? Posted by Tamar Granor @ 1/7/2008 11:05:53 PM
RE: count records of closed table? Posted by Ellen Solomon @ 1/9/2008 10:40:36 AM
RE: count records of closed table? Posted by Ellen Solomon @ 1/10/2008 9:13:28 AM
RE: count records of closed table? Posted by Tamar Granor @ 1/10/2008 11:16:40 PM
RE: count records of closed table? Posted by Ellen Solomon @ 1/11/2008 9:58:29 AM
RE: count records of closed table? Posted by Cetin Basoz @ 1/4/2008 1:59:06 PM
RE: count records of closed table? Posted by Mike Yearwood @ 1/5/2008 5:04:55 PM
RE: count records of closed table? Posted by Cetin Basoz @ 12/29/2007 10:52:11 PM
RE: count records of closed table? Posted by Eric den Doop @ 12/29/2007 10:53:06 PM
RE: count records of closed table? Posted by Amphie Lucas @ 1/4/2008 6:30:58 AM
RE: count records of closed table? Posted by Nishant Gupta @ 1/4/2008 2:30:07 PM