新项目在列末尾添加两次

Question

I am trying to update the store column by adding new item (string) to the end of the column, But what happens is the new item is added twice at the end of the column, This is the code:

$query = "SELECT * FROM users";
$result = $conn->query($query);

while($row = $result->fetch_assoc()){

$item = 'item_name';
$store = $row['store'];
$newstore = $store . '|' . $item;

echo 'newstore : ' . $newstore . '<br>'; // It looks normal : store|item
    
$sql = "UPDATE users SET store='" . $newstore . "' WHERE username='" . $row['username'] .  "'";
$conn->query($sql); 
}

In in the database I find: store|item|item

Answer 1

Rather than reading the entire table and looping through it with PHP, run just a single UPDATE query to concatenate the extra data onto the column.:

$item = 'item_name';
$query = "UPDATE users SET store=concat(store,'|','$item')";
$result = $conn->query($query);

Note: this form is potentially open to SQL injection if you can't trust the value in $item . You'd do better to use a prepared query if that's the case.