Getting error warning: mysql_num_rows(): supplied argument is not a valid MySQL result resource

Dear All,

Pls help. I am a newbie..I am getting an error like this "warning: mysql_num_rows(): supplied argument is not a valid MySQL result resource in /srv/www/htdocs/Sathish/includes/common.inc(1645) : eval()'d code on line 45."
I am trying to select the data from the DB . At that time ,I am getting the above error. Thanks for any help/