我想要理解我的GPA点列然后我想要分区与行完全求和

I want to SUM my GPA point Column And Then I want to Division full summation with rows, from database according to my column (Class=Secession=roll). Then I will echo full Grade. Please expert brother Help me. I am still learner. Thank You to all

this is my database

<?php  
        include 'connect.php';
        $class_n =$_POST['class_n'];
        $class_s =$_POST['class_s'];
        $r =$_POST['roll'];

        $sql="select SUM(point) AS gpa from full_result where class_n='$class_n' AND class_s='$class_s' AND roll='$r'";
        $data = mysql_query($sql);
        $c = $gpa / 5;
        echo $c;
?>

You need to extract out the gpa alias from your result set. In the original problem, you were using the variable $gpa which was never assigned.

$sql="select SUM(point) AS gpa from full_result where class_n='$class_n' AND class_s='$class_s' AND roll='$r'";
$data = mysql_query($sql);

$row = mysql_fetch_assoc($data);
$gpa = $row["gpa"];
$c = $gpa / 5;
echo $c;