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Using Perl and MySQL
Posted on 2002-06-03
I have written Perl code to access a MySQL database. I am changing the code to cache previously loaded web pages into a 4k text buffer in the database. The internet response is loaded into a variable called $response as follows:
$req=HTTP::Request->new("GET", $url);
$req->content_type('applic
$response=$ua->simple_requ
To save the information the following is done:
$respstr = $response->as_string;
$respstr1 = substr($respstr, 0, 4000);
$cachepage = $respstr1;
$sql = "update links set cachepage='$cachepage' where id=$id";
$tda = $dbh->prepare($sql) or die "Error preparing: ", $dbh->errstr;
$tda->execute or die "Error executing: ", $dbh->errstr;
The variable $cachepage is a text type in the MySQL database.
When the execute is attempted, no response is returned and I am sure it fails since the database is not written to.
Do I need to set a length work or something to get this to work? Thanks for any help.
$req=HTTP::Request->new("GET", $url);
$req->content_type('applic
$response=$ua->simple_requ
To save the information the following is done:
$respstr = $response->as_string;
$respstr1 = substr($respstr, 0, 4000);
$cachepage = $respstr1;
$sql = "update links set cachepage='$cachepage' where id=$id";
$tda = $dbh->prepare($sql) or die "Error preparing: ", $dbh->errstr;
$tda->execute or die "Error executing: ", $dbh->errstr;
The variable $cachepage is a text type in the MySQL database.
When the execute is attempted, no response is returned and I am sure it fails since the database is not written to.
Do I need to set a length work or something to get this to work? Thanks for any help.
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7 Comments
$tda->execute or die "Error executing: ", $dbh->errstr;
$dbh->commit; ## <- you need to commit the update.
$dbh->commit; ## <- you need to commit the update.
It still does not work even with $dbh->commit;. There is no error message, but unless the line:
$tda->execute or die "Error executing: ", $dbh->errstr;
is commented out the web page will not return output.
$tda->execute or die "Error executing: ", $dbh->errstr;
is commented out the web page will not return output.
Silly question...but are you connecting to the DB first?
You also should escape the single quotes
$sql = "update links set cachepage=\'$cachepage\' where id=$id";
I'm pretty sure this is the case...I did a project with MySQL once so this is from memory, also I don't have immediate access to some tools such as perl... In any case, it won't hurt....
One other thing, you shouldn't need to prepare that update statement. Just do:
$sql = "update links set cachepage=\'$cachepage\' where id=$id";
$dbh->do($sql);
if($DBI::err != 0) {
print "error here!\n";
print $dbh->errstr;
}
$dbh->commit;
Maybe something in there will move you in the right direction...
You also should escape the single quotes
$sql = "update links set cachepage=\'$cachepage\' where id=$id";
I'm pretty sure this is the case...I did a project with MySQL once so this is from memory, also I don't have immediate access to some tools such as perl... In any case, it won't hurt....
One other thing, you shouldn't need to prepare that update statement. Just do:
$sql = "update links set cachepage=\'$cachepage\' where id=$id";
$dbh->do($sql);
if($DBI::err != 0) {
print "error here!\n";
print $dbh->errstr;
}
$dbh->commit;
Maybe something in there will move you in the right direction...
Also add this to your script:
use CGI::Carp qw(fatalsToBrowser);
It will cause 'die' messages to go to your browser.
use CGI::Carp qw(fatalsToBrowser);
It will cause 'die' messages to go to your browser.
bluprint:
I am connecting to the database first since I am performing successful queries prior to the code I posted above.
dda:
I tried your suggestion. It worked with an interesting error. I stated that I have an error in my SQL syntax near 'Gave information here'.
The interesting thing about the information is that it is part of the string that I am writing to the database. This is why I suspect that it is a possible problem with the syntax of the variable being written. I have not used blob or text types (beyond 255 characters) with MySQL before.
I removed:
$respstr = $response->as_string;
and the program worked responded with the text output I placed at the end of it. It appeared to work, but I'm not sure the datbase contains the web page contents.
Therefore part of the problem was that I was converting it to a string before saving to the database. I'm not sure why this caused a problem. I still need to investigate to tell if the data was wriiten to the database. It does not appear in MySQL admin.
I am connecting to the database first since I am performing successful queries prior to the code I posted above.
dda:
I tried your suggestion. It worked with an interesting error. I stated that I have an error in my SQL syntax near 'Gave information here'.
The interesting thing about the information is that it is part of the string that I am writing to the database. This is why I suspect that it is a possible problem with the syntax of the variable being written. I have not used blob or text types (beyond 255 characters) with MySQL before.
I removed:
$respstr = $response->as_string;
and the program worked responded with the text output I placed at the end of it. It appeared to work, but I'm not sure the datbase contains the web page contents.
Therefore part of the problem was that I was converting it to a string before saving to the database. I'm not sure why this caused a problem. I still need to investigate to tell if the data was wriiten to the database. It does not appear in MySQL admin.
I bet you have single or souble quotes in yout text being inserted into database. You can mask them with '\' or, better way, use placeholders and parameters to execute():
$sql = "update links set cachepage=? where id=?";
$tda = $dbh->prepare($sql) or die "Error preparing: ", $dbh->errstr;
$tda->execute($cachepage, $id) or die "Error executing: ", $dbh->errstr;
$sql = "update links set cachepage=? where id=?";
$tda = $dbh->prepare($sql) or die "Error preparing: ", $dbh->errstr;
$tda->execute($cachepage, $id) or die "Error executing: ", $dbh->errstr;
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