Newbie question with Query

I'm having trouble with user validation. I have a query as follows: $query = mysql_query("SELECT * FROM clients WHERE CUserName=='$CUserName' AND CPassword=='$CPassword'"); if(!query) die ("Invalid username/password combo.") else print "Thank you for loggin in"; The problem is, it rejects a valid username/combo everytime. I am certain that there is a connection with MySQL and when I tried to do a print "$query" to see my result. It brings back nothing. In the SELECT statement, I tried to use only single "=" but it always logs the user in because i'm assigning the variables as equal AND the print "$query" displays resource id#2! Can someone help me out here? Thanks, Marc