Re: Need help with for loop, pulling MySQL data, completely lost

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



Evan Priestley wrote:
Dan,

When you run the second query ("$query1"), its results overwrite the results of your first query ("$query0"). `mysql_fetch_assoc()' returns results from the _most recent_ query, so after the first iteration, the call to `mysql_fetch_assoc()' is returning results from `query1', not from `query0'.

To solve this, retrieve all data from `query0' before iterating over it. Sample code in /painstakingly exact/ PHP which I have tested extensively:

<?"php"

run query0

while( rows exist )
    $rows[] = get next row

foreach $rows
    for i = 0; i >= 0; i-- {
       build query1
       run query1
       }
?>

Excellent description of your problem, by the way; this one's tricky and definitely had me for a while when I first ran into it.

Evan

On Aug 21, 2005, at 7:24 AM, Dan Trainor wrote:

Hello, all -

As a pet project of mine, I've decided to write a bit of code. This is what I have, and it's not working as expected:

if ($action == "prepareforupdate") {
    @unlink("UPDATES/".$id."/9.jpg");
    $query0    = "SELECT * FROM updates WHERE id=".$id."";
    if (!$dbdata = mysql_query($query0)) {
        echo "Can't run query:  ".mysql_error();
        die;
    };

    for ($i = 9; $i >= 0; $i--) {
        $j = $i - 1;

        echo "Getting ready to rename UPDATES/$id/$j.jpg to
          UPDATES/$id/$i.jpg || &nbsp;&nbsp;&nbsp;&nbsp;<br />";

        @rename("UPDATES/$id/$j.jpg","UPDATES/$id/$i.jpg");

        $returned = mysql_fetch_assoc($dbdata);

        $query1 = "UPDATE updates SET " . $i . "d = '"
          .$returned[$j."d"]. "' WHERE id='" . $id . "'";

        if (!mysql_query($query1)) {
            echo "MySQL Error:  ".mysql_error();
        };

    }
}


I have a database in the following format. Let's say that "d" stands for date, and "t" stands for times, and I have ten days' worth of archives going on:

|id|1d|1t|2d|2t|3d|3t|.......|8d|8t|9d|9t|

I'm trying to "move" the contents of the previous field to the logical next field, so the value of field "8d" becomes "9d", the value of "7t" becomes the value of "8t", and so on.

The problem that I'm having here is that only the first iteration of the for loop work properly. Everything after that, is not being pulled up properly, I suspect. This is what MySQL shows:

174 Query       SELECT * FROM updates WHERE id=5
174 Query       UPDATE updates SET 9d = '2005-08-21' WHERE id='5'
174 Query       UPDATE updates SET 8d = '' WHERE id='5'
....
174 Query       UPDATE updates SET 1d = '' WHERE id='5'
174 Query       UPDATE updates SET 0d = '' WHERE id='5'

So all in all, I think I might be a bit out of my league here, but I am eager to learn. I think of this as more of a dynamic approach to a situation that I'm trying to adapt to.

As always, any feedback, or flames for that matter, would be greatly appreciated.

Thanks
-dant

--
PHP General Mailing List (http://www.php.net/)
To unsubscribe, visit: http://www.php.net/unsub.php




Hello, Evan, and thanks for your reply -

I was under the impression that, since I specified $dbdata as the argument to mysql_fetch_assoc(), that this would work exclusively with query0. I'm a bit confused as to how query0's return is getting overwritten, since I've tried to keep query0 and query1 seperate.

I'm going to drop this whole script, since I've found a much better way of keeping records of updates involving one big-ass database, but I'd at least like to know what I did wrong in this instance, so that I at least learn something. Your explanation was very helpful, but please clarify, if you would be so kind.

Thanks
-dant

--
PHP General Mailing List (http://www.php.net/)
To unsubscribe, visit: http://www.php.net/unsub.php


[Index of Archives]     [PHP Home]     [Apache Users]     [PHP on Windows]     [Kernel Newbies]     [PHP Install]     [PHP Classes]     [Pear]     [Postgresql]     [Postgresql PHP]     [PHP on Windows]     [PHP Database Programming]     [PHP SOAP]

  Powered by Linux