Help with msql_fetch_array()

I have a couple of scripts that fail with the error of: Warning: mysql_fetch_array(): supplied argument is not a valid MySQL result resource in... I'm new to both SQL and PHP and I'm wondering if I have some setting turned off or what. Here's the piece of code that is failing (the second line fails): $result = mysql_db_query($dbname, "SELECT * FROM tablename ORDER BY id"); $row = mysql_fetch_array($result); Thanks for your help in advance!!