tag:blogger.com,1999:blog-3069349063312276662.post7506522708974301460..comments2009-10-07T02:25:09.744+02:00Comments on Insane Terminology: Selecting multiple random rows from table in rails...Robert Nasiadekhttp://www.blogger.com/profile/06721470947386818024noreply@blogger.comBlogger3125tag:blogger.com,1999:blog-3069349063312276662.post-53192429515414584572009-10-07T00:59:20.136+02:002009-10-07T00:59:20.136+02:00even chosen randomly, records would be displayed i...even chosen randomly, records would be displayed in order. For example random 3 ids from (1..10) would return 3,5,6 or 6,7,8. What would be the efficent way to mix that order ?gRubynoreply@blogger.comtag:blogger.com,1999:blog-3069349063312276662.post-22082274274366313022008-11-03T09:46:00.000+01:002008-11-03T09:46:00.000+01:00Not really. If you go like this, the database will...Not really. If you go like this, the database will first generate random number for EVERY row in the table, then sort by that number and choose n first rows. That's a performance killer.Robert Nasiadekhttp://www.blogger.com/profile/06721470947386818024noreply@blogger.comtag:blogger.com,1999:blog-3069349063312276662.post-45657815021662100312008-11-02T21:37:00.000+01:002008-11-02T21:37:00.000+01:00can't you just use :order => "RAND()", :limit => n...can't you just use :order => "RAND()", :limit => n<BR/><BR/>(exact syntax will vary by database.)dariushttp://www.blogger.com/profile/06890701761552832592noreply@blogger.com