Here is a simple patch for mysql_auth v0.8, a Squid HTTP proxy MySQL authentication module by Ervin Hegedus.
The patch enables the user to configure a additional part for the select-statement like 'is_active = 1'.
 
The patch may be downloaded from here!
 
You can apply the patch like this:

wget http://people.arxnet.hu/airween/mysql_auth/mysql_auth-0.8.tar.gz
tar xvzf mysql_auth-0.8.tar.gz
wget http://www.zero-sys.net/portal/download/additionalselect.patch
cd mysql_auth-0.8
patch -p1 < ../additionalselect.patch

More details on how to use mysql_auth can be found at the homepage of mysql_auth