From: Jan Steinman Date: July 15 2011 5:40pm Subject: MySQL RAND() Issues [was Re: How to Shuffle data] List-Archive: http://lists.mysql.com/mysql/225386 Message-Id: MIME-Version: 1.0 (Apple Message framework v1084) Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: quoted-printable > From: Reindl Harald >=20 > do not use any random-functions of mysql even if they exists > http://bugs.mysql.com/bug.php?id=3D59253 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 , 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 ::::