我正在尝试用输入到用户中的一些新值更新我的sql表。由于某些原因，sql命令没有更新我的数据库。我得到了我验证过的正确值。这是我的密码

# !/usr/bin/perl

# This is going to be the user login check and will set a cookie

use DBI;
use CGI qw(:standard);

use strict;

# Connection error

sub showErrorMsgAndExit {
    print header(), start_html(-title=>shift);
    print (shift);
    print end_html();
    exit;
}

# Connecting to the database

my $dbUsername = "root";
my $dbPassword = "password";

my $dsn = "DBI:mysql:f18final:localhost";
my $dbh = DBI->connect($dsn, $dbUsername, $dbPassword, {PrintError => 0});

# error checking

if(!$dbh) {
    print header(), start_html(-title=>"Error connecting to DB");
    print ("Unable to connec to the database");
    print end_html();
    exit;
}

print header;
print start_html(-title=>'Add Classes');

# Get the information the user entered

my $id = param('classid');
my $className = param('classname');
my $department = param('department');
my $classnum = param('classnum');
my $grade = param('grade');
my $credits = param('credit');
print "$id $className, $department, $classnum, $grade, $credits";

# first sql check to see if username is already taken

my $check = "UPDATE tblclasses(classname, department, classnum, grade, credits) VALUES (?, ?, ?, ?, ?) WHERE classID = $id";
my $sth = $dbh->prepare($check);
$sth->execute($className, $department, $classnum, $grade,$credits);
print "<h1>Success</h1>";
print "<form action=http://localhost/cgi-bin/edit.pl method = 'post'>";
print "<input type = 'submit' name = 'submit' value = 'Update Another'>";
print "</form>";
print "<form action=http://localhost/cgi-bin/actions.pl method = 'post'>";
print "<input type = 'submit' name = 'submit' value = 'Back to actions'>";
print "</form>";

print end_html();
exit;

当我尝试在mysql工作台中运行sql命令时，它成功地更新了行。我的问题是什么？