delete values in the database - PHP

Question

I should delete values from the database but end now, the only result that I managed to get is to make a certain value null, and then this then becomes invalid, but if I want to repeat the process I can no longer do it. My goal would be to freely delete all the products I want from a given event, place the code for deletion:

<a href="#elimina<?php echo $row['impianto_id_campagna']; ?>" data-toggle="modal" class="btn-floating btn-sm btn-pin "><span class="glyphicon glyphicon-trash"></span> <i class='fa fa-remove' aria-hidden='true'></i></a

modal:

<div class="modal fade" id="elimina<?php echo $row['impianto_id_campagna']; ?>" tabindex="-1" role="dialog" aria-labelledby="myModalLabel" aria-hidden="true"> <div class="modal-dialog" role="document"> <div class="modal-content"> <div class="modal-header text-center"> <h4 class="modal-title w-100 font-weight-bold">Elimina Impianto</h4> <button type="button" class="close" data-dismiss="modal" aria-label="Close"> <span aria-hidden="true">&times;</span> </button> </div> <?php $elimina=mysqli_query($connessione,"select * from campagne_cliente where impianto_id_campagna='".$row['impianto_id_campagna']."'"); $row_due=mysqli_fetch_array($elimina); ?> <div class="modal-body mx-3"> <h5 style="text-align: center;">Eliminare l'impianto dalla campagna?</h5> </div> <div class="modal-footer d-flex justify-content-center"> <a href="eliminainfo.php?impianto_id_campagna=<?php echo $row['impianto_id_campagna']; ?>" class="btn btn-danger"><span class="glyphicon glyphicon-trash"></span>Elimina</a> </div> </div> </div> </div>

delete_page:

<?php include '../../connessione.php'; $impianto_id_campagna=$_GET['impianto_id_campagna']; mysqli_query($connessione,"UPDATE campagne_cliente SET impianto_id_campagna = NULL WHERE impianto_id_campagna = '$impianto_id_campagna'"); header('location: campagne.php'); ?>

my db structure: my db structure

in the picture you will see a value set to 0, but if I later want to set another value to 0, I can not do it, the maximum would be to delete the whole row, starting from the id_impianto_campagna

I juste want to point out that putting $impianto_id_campagna directly inside the query without escaping is open for sql injection. Proper sanitization or prepared statement should be used. — taccola
– taccola, Commented Nov 3, 2018 at 20:43
As said by another user, your code is open to SQL injections, I updated my anwser below to show you something that you could use to prevent this. — rpm192
– rpm192, Commented Nov 3, 2018 at 20:58

rpm192 · Accepted Answer · 2019-03-02 20:02:08Z

You're using an UPDATE query where you should be using a DELETE query instead.

It should work if you replace this:

"UPDATE campagne_cliente SET impianto_id_campagna = NULL WHERE impianto_id_campagna = '$impianto_id_campagna'";

With this:

"DELETE * FROM campagne_cliente WHERE impianto_id_campagna = '$impianto_id_campagna'"

As said by other users, your code is open to SQL injections, use prepared statements instead.

// ... Set your connection variables $conn = new mysqli($host, $user, $password, $database); // Query $sql = "DELETE * FROM campagne_cliente WHERE impianto_id_campagna = ?"; $stmt = $conn->prepare($sql); if(!$stmt) { // ... Couldn't prepare statment, handle your error } $id = $_GET['impianto_id_campagna']; if(!$stmt->bind_param('i', $id)) { // ... Couldn't bind parameters, handle your error } if(!$stmt->execute()) { // ... Couldn't execute query, handle your error } else { echo 'Record deleted.'; }

engrhussainahmad · Accepted Answer · 2018-11-03 20:41:05Z

If you are deleting the record against primary key then replace:

"UPDATE campagne_cliente SET impianto_id_campagna = NULL WHERE impianto_id_campagna = '$impianto_id_campagna'"

with:

"DELETE FROM campagne_cliente WHERE impianto_id_campagna = $impianto_id_campagna"

and check it again.

Your answer could be improved by describing what your code does and why it solves the problem.

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