List:General Discussion« Previous MessageNext Message »
From:Jan Steinman Date:July 15 2011 5:40pm
Subject:MySQL RAND() Issues [was Re: How to Shuffle data]
View as plain text  
> From: Reindl Harald <h.reindl@stripped>
> 
> do not use any random-functions of mysql even if they exists
> http://bugs.mysql.com/bug.php?id=59253

Of course, it depends on the desired quality of randomness needed.

I'm using RAND() to select random quotations to put at the end of emails. I can easily
repeat the process by re-selecting the "Signature:" menu in Apple Mail. Problem is, I
often notice that doing so cycles through several similar signatures in a decidedly
non-random way!

(You can demo this by sending email to <Quote@stripped>, with a search term in
the Subject: line.)

But of course, a nuclear plant is not going to melt down because of my signature line.

So RAND() can be useful, but it is not really very random, and should be used with
caution. My guess is that it's using Knuth's linear congruential algorithm that has
well-known problems, but that unfortunately has been hidden deep in system code libraries
since "Fundamental Algorithms" was published in 1968.

----------------
World events tend to be driven by loose coalitions of economic, political, and military
interests, which function like guilds of species in an ecosystem. These guilds generate
patterns of events that meet the interests of these coalitions, without there being any
unity of purpose or clear plan. When powerful players accept they are not all-powerful,
they increase their effectiveness, but are also able to deny and cover any responsibility
for the adverse outcomes of those actions. -- David Holmgren
:::: Jan Steinman, EcoReality Co-op ::::

Thread
MySQL RAND() Issues [was Re: How to Shuffle data]Jan Steinman15 Jul
  • Re: MySQL RAND() Issues [was Re: How to Shuffle data]Arthur Fuller15 Jul
    • Re: MySQL RAND() Issues [was Re: How to Shuffle data]Michael Dykman15 Jul
    • Re: MySQL RAND() Issues [was Re: How to Shuffle data]Dan Nelson15 Jul
  • Re: MySQL RAND() Issues [was Re: How to Shuffle data]Reindl Harald15 Jul