我想总结两列的行，然后使用php update将值插入同一个表中的另一列的行。 可能吗？

Question

I want to sum two columns' row and then the value insert the other column;s row in the same table using php update. Is it possible?

I try many time but the updated value in all row are same. Like:

id-1, total-150
id-2, total-150
id-3, total-150

Now what can I do?

MySQL table looks like this:

My code :

<?php
$conn= new mysqli("localhost", "root", "", "zidm");                      

$sql = "SELECT * from exam_model "; 
foreach ($conn->query($sql) as $row){  
    $total= $row['English'] + $row['Math']; 

    $sql="UPDATE exam_model SET total='$total' ";
    mysqli_query($conn,$sql);
}
?>

Answer 1

you missing WHERE clauses.

<?php   
$conn= new mysqli("localhost", "root", "", "zidm");                     

$sql = "SELECT * from exam_model ";
foreach ($conn->query($sql) as $row){  
    $total= $row['English'] + $row['Math']; 
    $id = $row['id'];<br> 
    $sql="UPDATE exam_model SET total='$total' WHERE id = $id"; 
    mysqli_query($conn,$sql); 
}
?>

Answer 2

If you need an update on single row you should add a where clause eg:

<?php
  $conn= new mysqli("localhost", "root", "", "zidm");          


    $sql = "SELECT * from exam_model "; 
    foreach ($conn->query($sql) as $row)  
    {  
      $total= $row['English'] + $row['Math']; 
      $id = $row['id'];

      $sql="UPDATE exam_model SET total='$total'  WHERE id = $id";
      mysqli_query($conn,$sql);
    }

?>