pam_mysql always sends "pam_mysql - SELECT returned no result." to syslog, even if verbose=0.
I don't think there's a reason for keeping this line in the logs once the configuration debugging is done, as it is a normal situation when the user is provided by an other PAM module.
The provided patch simply adds a test before each call to the syslog() function that prints "SELECT returned no result." It was made against pam_mysql.c of pam_mysql 0.7-RC1.
patch for 0.70-RC1 to avoid logging ''SELECT returned no result."