From: Michael Dykman Date: July 15 2011 6:42pm Subject: Re: MySQL RAND() Issues [was Re: How to Shuffle data] List-Archive: http://lists.mysql.com/mysql/225389 Message-Id: MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable I have found this approach pretty effective: select *, rand() r from [mytable] where [condition] order by r limit 1= 0 as long as you are aware that a random number is generated for every row in the table. - michael dykman On Fri, Jul 15, 2011 at 2:12 PM, Arthur Fuller wr= ote: > This would be sooo much simpler to solve in MS-SQL, given the function > NewID(), which is guaranteed to return a unique value. I have used this i= n a > few web sites and it works splendidly; something along the lines of > > SELECT TOP 10 *, NewID() FROM User_Messages > ORDER BY NewID > > which is guaranteed to produce a new GUID for each row, and then order by > said values. It is not guaranteed to produce 10 results different than th= e > previous SELECT, but nevertheless works extremely well on a web site. > > I have Googled this and that but not yet succeeded in finding the equival= ent > in the MySQL world. In theory, this should be relatively easy, since the > GUID docs are available, but I'm out of my depth here on how to write the > MySQL equivalent function. > > In case anyone has devised a MySQL equivalent for the NewID() function, w= e > could all massively benefit from your posting of same. > > TIA, > Arthur > > On Fri, Jul 15, 2011 at 1:40 PM, Jan Steinman wrote: > >> > From: Reindl Harald >> > >> > 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 A= pple >> 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 congruenti= al >> 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, politica= l, >> and military interests, which function like guilds of species in an >> ecosystem. These guilds generate patterns of events that meet the intere= sts >> of these coalitions, without there being any unity of purpose or clear p= lan. >> When powerful players accept they are not all-powerful, they increase th= eir >> effectiveness, but are also able to deny and cover any responsibility fo= r >> the adverse outcomes of those actions. -- David Holmgren >> :::: Jan Steinman, EcoReality Co-op :::: >> >> >> -- >> MySQL General Mailing List >> For list archives: http://lists.mysql.com/mysql >> To unsubscribe: >> http://lists.mysql.com/mysql?unsub=3Dfuller.artful@stripped >> >> > --=20 =A0- michael dykman =A0- mdykman@stripped =A0May the Source be with you.