Increment a value in MySQL with PHP/MySQL?
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I have a posting system, When the user post's I want the postcount row in the table to increase by one.  I have researched on google and on here and I have only found this.

    mysql_query("UPDATE users SET postcount=postcount+1 WHERE username = '$username'");
I have also tried it with spaces 

    mysql_query("UPDATE users SET postcount = postcount + 1 WHERE username = '$username'");
And no such luck, I'm not seeing the number in the table increasing. 
Help?
Thanks!