I would use a PRNG with limits set for the full size of your data set and extract a rowids and select that rows then store the seed and iterate 500 times, or whatever the size of your sample. That should give you a random distribution.
Barbara Weinberg 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. > > > 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. >> >> _______________________________________________ >> 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 _______________________________________________ sqlite-users mailing list sqlite-users@sqlite.org http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users
