Chec db if username is already there

Hello, I am fairly new to php and need some help. I have written a sign-up and need to find out if the user name and or the email address are already in the database. The second thing is, I am at the point where I am trying to write a little more less verbose. Is they a shorter way of writing the mail function, then what I have. IT Gary //Send Email From Form $msg = "Your UserName Is:\t$username\n"; $msg .= "Your Password Is:\t$password\n"; $msg .= "Please save this mail for future reference. Thank you for joining\n\n"; $headers = "From:\"Membership\"<Me@mydomain.com>\n"; mail("$email", "Thanks for joining", $msg, $mailheaders); //Put The Info In The Database $db = mysql_connect("localhost","user","password") or die ("couldn't connect to server"); mysql_select_db("dbname",$db) or die ("couldn't select database"); $sql = "INSERT INTO members(username,password,email) VALUES ('$username','$password','$email')"; $result = mysql_query($sql); if (!$result) { echo "<h2>couldn't add record</h2>"; } else { echo "<center><h1>Thank You $username<br> for Joining</h1></center>"; }