Does this mysql code work for deleting people's PMs if they have only 1 PM?

[SnickersTK]

been making this code and I admit that I am very new to mysql, so it might not make sense.

I haven't dared to try it out.

PHP Code:

<?php
$connection = mysql_connect("localhost", "username", "password");
   mysql_select_db("database", $connection); //connect to server and select database
   
require ("global.php"); 
$time = time() - (60 * 24 * 60 * 60);

$userid_result = query("SELECT `userid` ' 
        . ' FROM `user` ' 
        . ' WHERE `pmtotal` = 1 ' 
        . ' INTERSECT '
        . ' Select `fromuserid` ' 
        . ' FROM `pmtext` ' 
        . ' WHERE `dateline` < $time");
        //Make sure that the user-ids selected with 1 total PM only gets choosen if the PM is 60 days old.  


$sql = ' TRUNCATE `*` ' 
        . ' FROM `pm` ' 
        . ' WHERE `userid` = $userid_result';
         
$sql = 'TRUNCATE `*` ' 
        . ' FROM `pmtext` ' 
        . ' WHERE `fromuserid` = $userid_result'; 
         
MySQL_query($sql) or die('MySQL Failed Because: ' . mysql_error()); 

?>

Any assistance is greatly appreciated. I think it is a nice hack. I am running a giant board and all members who signs up gets an welcome PM (very popular and I don't want to get rid of it)