update multiple rows with calculated variable

Question

The table_calc structure (minimized) is:

| id | value_1 | value_2 |

the number of rows is between 70 and 250 or more.

I want to update the fields in "table_calc" with values resulting from other calculations ($value_update_1 and 2, ...), values applied different to the fields in the table.

Before I used a table on the web page and from there I updated the table. Now I want to update the values directly without having to take them in the page, as it should work.

I started to write the code below:

$stmt_update = $conn_bd->prepare('select * from table_calc');
$stmt_update->execute(array());
$result_stmt_update = $stmt_update->fetchAll();
foreach($result_stmt_update as $rrows_update) {
  $cal_id = $rrows_update[id];
  $cal_value_1 = $rrows_update['value_1'];
  $cal_value_2 = $rrows_update['value_2'];
}

$value_update_1 = 100.25;
$value_update_2 = 150.25;

$count_id = count($cal_id);
$stmt = $conn_bd->prepare('UPDATE table_calc SET value_1 = :value_1, value_2 = :value_2 WHERE id = :id');
$i = 0;
while($i < $count_id) {
  $stmt->bindParam(':value_1', '.$cal_value_1[$i].' * '.$value_update_2.');
  $stmt->bindParam(':value_2', '.$cal_value_2[$i].' * '.$value_update_1.');
  $stmt->bindParam(':id', $cal_id[$i]);
  $stmt->execute();
  $i++;
}

but it doesn't work

Can you help?

Answer 1

I can spot a few issues on your code:

• On line 8:

   $cal_id = $rrows_update[id]; ^^ 

  You need quotes there.

• On line 20, you call your variable as if it were an array, but you don't set it as such on lines 9-10.
• Again on line 20, you should bind the final value to the parameter, not leave it to be evaluated by MySQL.

So the corrected version would be:

$stmt_update = $conn_bd->prepare('select * from table_calc');
$stmt_update->execute(array());
$result_stmt_update = $stmt_update->fetchAll();
foreach ($result_stmt_update as $rrows_update) {
    //Added array push operators. To make them arrays.
    $cal_id[]      = $rrows_update["id"];
    $cal_value_1[] = $rrows_update['value_1'];
    $cal_value_2[] = $rrows_update['value_2'];
}

$value_update_1 = 100.25;
$value_update_2 = 150.25;

$count_id = count($cal_id);
$stmt     = $conn_bd->prepare('UPDATE table_calc SET value_1 = :value_1, value_2 = :value_2 WHERE id = :id');
$i        = 0;
while ($i < $count_id) {
    //Altered the binding so that you bind the final value.
    //Also changed to bindValue.
    $stmt->bindValue(':value_1', $cal_value_1[$i] * $value_update_2);
    $stmt->bindValue(':value_2', $cal_value_2[$i] * $value_update_1);
    $stmt->bindValue(':id', $cal_id[$i]);
    $stmt->execute();
    $i++;
}

Also, when making batch changes to the database, you may want to use Transactions , to make sure all changes are registered as expected.