I ran into this same type of question the other evening at a local linux group.
I think that once you reach the end of the results set the only way to start back at the beginning of that results set is to do the query again. Once option - do your query and grab all the rows load them into a data structure - ie - a list of associative arrays Then all you need to do is incrementally go through the array. when you hit the end, just reset the index back to 0. -----Original Message----- From: Steffan A. Cline [mailto:[EMAIL PROTECTED] Sent: Friday, May 12, 2006 2:52 PM To: mysql@lists.mysql.com Subject: Re: Returning records in a circle Well, basically it can be done to an extent in some kind of code. Basically I am drawing from a table 2 records at a time. I want to make sure that all records are pulled at least once. If at all possible not to have 2 from the same vendor. So, in this case. I have columns id, html, vendor So I can add columns as needed. I tried adding a flag and after returning to the client the 2 records I'd mark it as flag = 1 then search like this Select id, html from urls order by flag, id desc limit 3 Then after I have those I would then set the last of the 3 to flag = 1 so that on the next search I get the 2 after. In theory it worked fine but when multiple people hit the page simultaneously I had flags in different places and not in order. Maybe just mark them as flag = 1 after returned and then on search if found is 0 then set all to flag = 0 so they can be seen again? This doesn't seem so bad but them I guess I'd use distinct? If I cant use distinct with other parameters... ex: select id,html distinct(vendor) from urls where flag=0 limit 2; Would it be like : Select id,html from urls where flag = 0 group by distinct(vendor) limit 2 ? Thanks Steffan --------------------------------------------------------------- T E L 6 0 2 . 5 7 9 . 4 2 3 0 | F A X 6 0 2 . 9 7 1 . 1 6 9 4 Steffan A. Cline [EMAIL PROTECTED] Phoenix, Az http://www.ExecuChoice.net USA AIM : SteffanC ICQ : 57234309 The Executive's Choice in Lasso driven Internet Applications Lasso Partner Alliance Member --------------------------------------------------------------- > From: Rhino <[EMAIL PROTECTED]> > Date: Fri, 12 May 2006 14:20:10 -0400 > To: "Steffan A. Cline" <[EMAIL PROTECTED]>, <mysql@lists.mysql.com> > Subject: Re: Returning records in a circle > > > ----- Original Message ----- > From: "Steffan A. Cline" <[EMAIL PROTECTED]> > To: <mysql@lists.mysql.com> > Sent: Friday, May 12, 2006 1:38 PM > Subject: Returning records in a circle > > >> Is there a way I can get a set of records incrementally such as to get 2 >> then the next query get the next 2 then at the end of all records to get >> the >> 2 from the beginning? I need to keep going incrementally by 2 in a circle. >> > > Are you trying to get these rows purely via SQL at the command line or in an > SQL script? Or would an application be an option for you? > > If you are not willing to consider application code to grab the rows you > want, the answer to your question is "maybe". SQL has always been intended > to return ALL of the rows that satisfy a query with a single invocation of > the query, no matter how many rows that is. So if your query says: > > select * from mytab; > > you will normally get all of the rows that satisfy that query in one go, > whether there are 0 rows, 100 rows, or a 100 million rows in the result. > > You _might_ be able to get the results you want by using the LIMIT clause. > I'm not sure what version of MySQL you are using but the LIMIT clause is > described in the MySQL 3.23/4.0/4.1 manual on this page: > http://dev.mysql.com/doc/refman/4.1/en/select.html. The problem is that > you'll still pretty much need some sort of script in order to keep executing > the query to get the next two records and you may need to change the > parameters of the LIMIT clause at the same time. > > If you are willing to write application code, things get a lot easier. For > instance, a Java program could easily grab rows from a result set for you > two at a time, let you process them, then grab two more, etc. I expect that > it would similarly easy to do the same thing in Perl and PHP and C. > > In short, a program gives you a lot more ability to do what you want to do > with your database data. But some shops have very little programming > expertise and prefer to do everything via SQL. If you work for one of those > shops, you might not be able to get your records two at a time with SQL > alone, unless you can write a script that takes advantage of the LIMIT > clause. > > I don't pretend to know MySQL exhaustively so someone else may have another > suggestion for you but the only two approaches I can think of that might > meet your needs are to use the LIMIT clause or to write an application. > > -- > Rhino > > > > > -- > No virus found in this outgoing message. > Checked by AVG Free Edition. > Version: 7.1.392 / Virus Database: 268.5.6/337 - Release Date: 11/05/2006 > -- MySQL General Mailing List For list archives: http://lists.mysql.com/mysql To unsubscribe: http://lists.mysql.com/[EMAIL PROTECTED] -- MySQL General Mailing List For list archives: http://lists.mysql.com/mysql To unsubscribe: http://lists.mysql.com/[EMAIL PROTECTED]
