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/$i.jpg || <br />";
@rename("UPDATES/$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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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
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