need help in mysql_num_rows()

[doforumda]

please tell me what i am doing wrong in this query. it displays this error

 

Warning: mysql_num_rows(): supplied argument is not a valid MySQL result resource in D:\wamp\www\dynamic\quiz2.php on line 77

 

my query is

$namecheck = mysql_query("select * from cv where name = '$name',apply='$apply' and email='$email'");
$countname = mysql_num_rows($namecheck);

if($countname != 0)
{
die("You have already applied for this vacancy.");
}

[trq]

SELECT * FROM cv WHERE name = '$name' AND apply='$apply' AND email='$email'