Simple Login Script

[Anon]

Ok, so now im working on a personal site of mine and I am in a little bit of coding trouble. How can I get php to check if a username exsists in a MySQL database?

[Anon]

$db_name="authorize";
$table_name="auth_users";
$connection = mysql_connect("localhost", "john", "camaro") or die ("no connection");
$db = mysql_select_db($db_name, $connection) or die ("no selection");
$sql = "select * from $table_name where username = \"$username\" and password = password(\"$password\")";
$result = mysql_query($sql,$connection) or die ("no executy");
$num = mysql_numrows($result);
if ($num != 0) {
echo "oh yeah logged in";
} else {
echo "Keep your hands out my cookie jar";

}