<div class="my-2">
<v-btn small color="primary">Primary</v-btn>
</div>
<link rel="stylesheet" href="https://fonts.googleapis.com/css?family=Roboto:100,300,400,500,700,900">
<link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/@mdi/font@latest/css/materialdesignicons.min.css">
<select name="cars" class="selectpicker" id="carList">
$result=mysqli_query($mysqli_connection, "SELECT * FROM shop WHERE id=2 FOR UPDATE");
$data=mysqli_fetch_assoc($result);
/* Что-нибудь делаем с данными... */
mysqli_query($mysqli_connection, "UPDATE shop SET amount={$data['amount']} WHERE id=2");