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Posted by Evan Priestley on 08/21/05 18:06
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/$i.jpg || <br />";
>
> @rename("UPDATES/$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
>
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