Delete MySql Entry

Okay, I'm making a recruit script for my gaming clan site. What it does, is when someone want's to recruit anyone they get a code that's generated and that code is placed into a table so when the member registers they use the code to verify themselves. I have all of it done, but now I need to delete the key so that it can be used again. Here is what I am using:

Code:

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$query="delete from codes where code = " . $key;
mysql_query($query);

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I have a table named "codes" and the two parts in it are "id" and "code". $key is the entered key from the registering member.

So I tested it myself, and even copied a code from the table and it still won't delete. What's wrong?

try

PHP Code:

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$query="delete from codes where code = '" . $key . "'"; 


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