How can I determine if a specified string is in a specific MySQL column? (and also perhaps a tutorial site?)

Question

This is a fairly simple question. Basically, I'm having a program send HardWare ID's to my PHP script as GET data. I need the PHP script check to make sure that HardWare ID is in a specific MySQL column, and if it is, { continue the script, } else { exit(); }

Problem is I'm not too good with MySQL and have no idea how to do this. However, I feel that I should know this by now, so if someone could also link me to a good tutorial site for MySQL, that kind of keeps it "humanized" if you know what I mean. One that "dumbs it down." I'm not dumb or anything, I just get sidetracked easily, and if all its doing is showing me code and not explaining it, I won't pick it up. If you don't have any tutorial sites off the top of your head, I'll settle for help with the first question, and try to hunt down a tutorial later.

EDIT: It was noted that it may help to see how my database is set up. I have a table called "hwids" In this table there are 3 columns: "id" "hwid" and "paypal"

(They buy the program from me, I add their HWID to the database so they can use the program. If they chargeback and try to scam me, I can easily check which HWID is assigned for the paypal that did a chargeback, and remove it from the system via a management page)

Answer 1

When I started learning PHP/MySQL, I really liked the books that O'Reilly publishes on the subject. You may want to check out Learning PHP, MySql, and Javascript. The official sites for PHP and MySql provide a lot of good links and information, as well as documentation. Tizag has a useful tutorial.

To answer your question a little, you could do a select query that checks if the number of rows found is greater than zero. i.e.:

$query = "SELECT * FROM hwids WHERE hwid = 'hardware_id'";
$result = mysql_query($query);
$num = mysql_num_rows($result);
if ($num > 0)
{
    // continue script
}
else 
{
    // exit/inform user
}

Answer 2

There are a number of steps you need to go through to achieve your goal, Breaking them up and learning each will help with your attention span (no disrespect I have the same problem)

Steps required to achieve your goal

1. Connect to MySql database - see documentation on mysql_connect and mysql_select_db
2. Validate your input (ensure you have a valid Hardware ID)
3. Prepare a query - I would suggest something like $Sql=sprintf("Select [columnName] from [tableName] where [columnName]=%s", mysql_escape_string($hardwareID));
4. get the recordset back by using mysql_query($sql) -see documentation on php.net
   5.Check see if it is empty mysql_num_rows() if so exit script

Hope that helps a resource I would point you at would be http://tuxradar.com/practicalphp particularly Chapter 9

All as others have put above really I was a little slow typing :)