Интерфейс программы

echo '
            <p><strong>Delete:</strong></p>
            <form method="post">
                productId: <input type="text" name="prodIdDel">
                <input type="submit" name=delete value="delete">
            </form>
        ';}

if (isset($_POST['delete']) && !empty($_POST['delete'])) {
        $del = mysqli_real_escape_string($_POST['prodIdDel']);
        $sql = "DELETE FROM products WHERE productId = '$del'";
        mysqli_query($con, $sql);
        echo "удалено!";
    }

$del = mysqli_real_escape_string($con, $_POST['productId']);

if (isset($_GET['search'])){
        $prodPrice = $_GET['search'];
        //2
        $sql = "SELECT * FROM products WHERE products.price > (SELECT AVG(Price) FROM Products)";
    }
    else $sql = "SELECT * FROM products";
    $result = mysqli_query($con, $sql);
    echo mysqli_error($con);
 
 <form action="products.php" method="get">
    <p>найдем товары из таблицы Products, которые имеют цену выше средней:</p>
    <input type="text" name="search" placeholder="input price">
    <input type="submit" value="search">
</form>

 if (isset($_GET['search'])){
        $minPrice = $_GET['search'];
        $sql = "SELECT * FROM products WHERE products.price = SELECT MIN('".$minPrice."') FROM products";
    }
    else $sql = "SELECT * FROM products";
    $result = mysqli_query($con, $sql);
    echo mysqli_error($con);

     SELECT * FROM `products` WHERE Price > (SELECT AVG(Price) FROM Products)
 
     (SELECT AVG(Price) FROM `products`)
     SELECT * FROM `products` WHERE price > (SELECT AVG(price) FROM `products`);
     SELECT * FROM `products` WHERE price = (SELECT MIN(price) FROM `products`);
 
     SELECT customers.firstName, products.price, orders.customerId FROM `orders`, `customers`, `products` 
     WHERE orders.customerId = customers.id AND orders.productId=products.productId
 
     SELECT customers.firstName, customers.secondName,
     products.productCount, products.price FROM `orders` 
     LEFT JOIN `customers` ON orders.customerId = customers.id
     LEFT JOIN `products` ON orders.productId = products.productId
     WHERE products.price > 7000
     ORDER BY products.createAt