The 40000 is the subset that my "where clause" cuts it down to. Not so relevant perhaps/ Where is your perl script. I would love to see it. Many thanks!
B On Thu, May 8, 2008 at 10:44 AM, P Kishor <[EMAIL PROTECTED]> wrote: > On 5/8/08, Barbara Weinberg <[EMAIL PROTECTED]> wrote: > > This is my query: > > select phn,random() as ran from demographics where sex='F' and dob >= > > 19400401 and dob <=19450331 order by ran limit 500 > > The original table has 7 million records and I am trying to select a > subset > > of about 40000 and sort them in random order. I am doing this to get a > > random 500 records. > > I don't know what the 40000 is doing there, but I would first select > all the records, and then shuffle them in memory outside the db. > > As I showed in my Perl script, it will be way much faster to do so. > > > > > > > > > > On Thu, May 8, 2008 at 9:17 AM, John Stanton <[EMAIL PROTECTED]> > wrote: > > > > > Dennis Cote wrote: > > > > Barbara Weinberg wrote: > > > >> I was wondering whether anyone had tried sorting records in random > > > order > > > >> using sqlite3. I tried sorting by random() and randomblob() but it > was > > > very > > > >> slow and chewed up lots of resources. Any suggestions? > > > > > > > > Can you provide any more details about what you are trying to > > > accomplish? > > > > > > > > There have been several previous discussions about selecting random > > > > records from a table. You may want to look for those in the > archives. If > > > > you really need to sort the entire table then you are probably > stuck > > > > with the slow operation. If you only need a random subset of a > table > > > > then you may be able to use some of these ideas to speed things up. > > > > > > > > HTH > > > > Dennis Cote > > > > > > > > > > If you have sequential rowids and know the largest then you can use a > PRNG > > > and get a random rowid to lookup. That will be optimally fast. > > > > > > > -- > Puneet Kishor http://punkish.eidesis.org/ > Nelson Institute for Environmental Studies http://www.nelson.wisc.edu/ > Open Source Geospatial Foundation (OSGeo) http://www.osgeo.org/ > _______________________________________________ > sqlite-users mailing list > sqlite-users@sqlite.org > http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users > _______________________________________________ sqlite-users mailing list sqlite-users@sqlite.org http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users
