Comments on: Generating numbers out of seemingly thin air http://code.openark.org/blog/mysql/generating-numbers-out-of-seemingly-thin-air Blog by Shlomi Noach Wed, 01 Feb 2012 20:47:51 +0000 hourly 1 http://wordpress.org/?v=3.3.1 By: shlomi http://code.openark.org/blog/mysql/generating-numbers-out-of-seemingly-thin-air/comment-page-1#comment-3641 shlomi Wed, 02 Sep 2009 03:38:45 +0000 http://code.openark.org/blog/?p=1148#comment-3641 @adj4096 Would you care to elaborate? If so, you can use the INFORMATION_SCHEMA tables. @adj4096

Would you care to elaborate?
If so, you can use the INFORMATION_SCHEMA tables.

]]> By: ajd4096 http://code.openark.org/blog/mysql/generating-numbers-out-of-seemingly-thin-air/comment-page-1#comment-3637 ajd4096 Tue, 01 Sep 2009 23:02:59 +0000 http://code.openark.org/blog/?p=1148#comment-3637 Don't be so sure that the help tables are *always* installed. Don't be so sure that the help tables are *always* installed.

]]> By: Rob Wultsch http://code.openark.org/blog/mysql/generating-numbers-out-of-seemingly-thin-air/comment-page-1#comment-3631 Rob Wultsch Tue, 01 Sep 2009 15:24:18 +0000 http://code.openark.org/blog/?p=1148#comment-3631 A much cleaner way of doing what is described above can be found in generate_series ( http://www.postgresql.org/docs/8.4/static/functions-srf.html ) which is found in a different free RDMS... A much cleaner way of doing what is described above can be found in generate_series ( http://www.postgresql.org/docs/8.4/static/functions-srf.html ) which is found in a different free RDMS...

]]> By: Toby http://code.openark.org/blog/mysql/generating-numbers-out-of-seemingly-thin-air/comment-page-1#comment-3630 Toby Tue, 01 Sep 2009 13:18:23 +0000 http://code.openark.org/blog/?p=1148#comment-3630 strcmp, It can be phrased as a self join, but may not be efficient (even quadratic): https://slashdot.org/~toby/journal/199210 strcmp, It can be phrased as a self join, but may not be efficient (even quadratic): https://slashdot.org/~toby/journal/199210

]]> By: strcmp http://code.openark.org/blog/mysql/generating-numbers-out-of-seemingly-thin-air/comment-page-1#comment-3629 strcmp Tue, 01 Sep 2009 12:52:39 +0000 http://code.openark.org/blog/?p=1148#comment-3629 as a former assembler and C programmer and number cruncher iterative code like "@counter := @counter + 1" looks suboptimal to me, because it is a data dependency between the iterations, forcing the code to be executed serially. of course that's just me and a totally useless comment right now, but even MySQL may once leave the stone ages and execute JOINs and table/index scans in parallel... bulk operations 'feel' better. as a former assembler and C programmer and number cruncher iterative code like "@counter := @counter + 1" looks suboptimal to me, because it is a data dependency between the iterations, forcing the code to be executed serially. of course that's just me and a totally useless comment right now, but even MySQL may once leave the stone ages and execute JOINs and table/index scans in parallel... bulk operations 'feel' better.

]]> By: shlomi http://code.openark.org/blog/mysql/generating-numbers-out-of-seemingly-thin-air/comment-page-1#comment-3625 shlomi Tue, 01 Sep 2009 11:15:56 +0000 http://code.openark.org/blog/?p=1148#comment-3625 @Giuseppe, Thanks for the references; Very interesting! @Mark, What a coincidence! @strcmp, My personal view is that shorter is usually better. Your solution has the property of choosing exactly 1000 thousand values, though. @Giuseppe,
Thanks for the references; Very interesting!

@Mark,
What a coincidence!

@strcmp,
My personal view is that shorter is usually better. Your solution has the property of choosing exactly 1000 thousand values, though.

]]> By: strcmp http://code.openark.org/blog/mysql/generating-numbers-out-of-seemingly-thin-air/comment-page-1#comment-3619 strcmp Tue, 01 Sep 2009 09:14:47 +0000 http://code.openark.org/blog/?p=1148#comment-3619 I mostly use UNIONs for this purpose: SELECT a.x*100+b.x*10+c.x FROM ( SELECT 0 x UNION ALL SELECT 1 UNION ALL SELECT 2 UNION ALL SELECT 3 UNION ALL SELECT 4 UNION ALL SELECT 5 UNION ALL SELECT 6 UNION ALL SELECT 7 UNION ALL SELECT 8 UNION ALL SELECT 9 ) a, ( SELECT 0 x UNION ALL SELECT 1 UNION ALL SELECT 2 UNION ALL SELECT 3 UNION ALL SELECT 4 UNION ALL SELECT 5 UNION ALL SELECT 6 UNION ALL SELECT 7 UNION ALL SELECT 8 UNION ALL SELECT 9 ) b, ( SELECT 0 x UNION ALL SELECT 1 UNION ALL SELECT 2 UNION ALL SELECT 3 UNION ALL SELECT 4 UNION ALL SELECT 5 UNION ALL SELECT 6 UNION ALL SELECT 7 UNION ALL SELECT 8 UNION ALL SELECT 9 ) c I don't know what's better. You don't need more priviledges for this than SELECT and it works with 4.1, but of course that puts more load onto the parser and you have much more UNIONs. I'm hoping that generating the bulk of the data with JOINs uses optimized code in the MySQL server like the JOIN buffer and temporary tables and that the overhead doesn't matter any more. I mostly use UNIONs for this purpose:

SELECT a.x*100+b.x*10+c.x
FROM (
SELECT 0 x UNION ALL SELECT 1 UNION ALL SELECT 2 UNION ALL SELECT 3 UNION ALL SELECT 4 UNION ALL SELECT 5 UNION ALL SELECT 6 UNION ALL SELECT 7 UNION ALL SELECT 8 UNION ALL SELECT 9
) a, (
SELECT 0 x UNION ALL SELECT 1 UNION ALL SELECT 2 UNION ALL SELECT 3 UNION ALL SELECT 4 UNION ALL SELECT 5 UNION ALL SELECT 6 UNION ALL SELECT 7 UNION ALL SELECT 8 UNION ALL SELECT 9
) b, (
SELECT 0 x UNION ALL SELECT 1 UNION ALL SELECT 2 UNION ALL SELECT 3 UNION ALL SELECT 4 UNION ALL SELECT 5 UNION ALL SELECT 6 UNION ALL SELECT 7 UNION ALL SELECT 8 UNION ALL SELECT 9
) c

I don't know what's better. You don't need more priviledges for this than SELECT and it works with 4.1, but of course that puts more load onto the parser and you have much more UNIONs. I'm hoping that generating the bulk of the data with JOINs uses optimized code in the MySQL server like the JOIN buffer and temporary tables and that the overhead doesn't matter any more.

]]> By: Mark http://code.openark.org/blog/mysql/generating-numbers-out-of-seemingly-thin-air/comment-page-1#comment-3618 Mark Tue, 01 Sep 2009 08:03:16 +0000 http://code.openark.org/blog/?p=1148#comment-3618 Interesting stuff about the help_topic table, thanks. I'd just worked out how to calculate the Fibonacci sequence on my blog (using one of my defined tables to join against) as part of my investigation into solving problems on the Euler project. http://www.oxfordtechnotes.co.uk/sqlblog/blog4.php/2009/08/29/project-euler-q2-with-mysql I may well use the help_topic table in future. Interesting stuff about the help_topic table, thanks. I'd just worked out how to calculate the Fibonacci sequence on my blog (using one of my defined tables to join against) as part of my investigation into solving problems on the Euler project. http://www.oxfordtechnotes.co.uk/sqlblog/blog4.php/2009/08/29/project-euler-q2-with-mysql I may well use the help_topic table in future.

]]> By: Giuseppe Maxia http://code.openark.org/blog/mysql/generating-numbers-out-of-seemingly-thin-air/comment-page-1#comment-3617 Giuseppe Maxia Tue, 01 Sep 2009 07:54:06 +0000 http://code.openark.org/blog/?p=1148#comment-3617 On the same vein, you may like these two posts: http://datacharmer.blogspot.com/2007/12/data-from-nothing-solution-to-pop-quiz.html http://datacharmer.blogspot.com/2007/12/pop-quiz-with-prize-generate-4-billion.html Giuseppe On the same vein, you may like these two posts:

http://datacharmer.blogspot.com/2007/12/data-from-nothing-solution-to-pop-quiz.html
http://datacharmer.blogspot.com/2007/12/pop-quiz-with-prize-generate-4-billion.html

Giuseppe

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