php - delete the data from database for multiple table

Below is my code forDELETE

<?php
session_start();
include('database.php');
$sql = "DELETE from (
    DELETE from `class8`
    UNION
    DELETE from `class9` 
    UNION
    DELETE from `class10` 
    UNION
    DELETE from `class11` 
    UNION
    DELETE from `class12`
    ) classes
    WHERE classes.teacher_id = :id";
$stmt = $conn->prepare($sql);
$stmt->bindParam(':id', $_SESSION['teacher_id']);   

    if($stmt->execute())
    {
        echo "<script type='text/javascript'> alert('delete sucessfull');
        window.location='prospectcorse.php';
        </script>";
    }

    else
    {
        echo "<script type='text/javascript'> alert('error');
        window.location='prospectcorse.php';
        </script>";
    }

?>
Copy code

Below is the error I get

Fatal error: Uncaught PDOException: SQLSTATE[42000]: Syntax error or access violation: 1064 You have an error in your SQL syntax; check the manual that corresponds to your MariaDB server version for the right syntax to use near 'UNION DELETE fromclass9 UNION DELETE fromclass10 UNI' at line 2 in C:\xampp\htdocs\kridha\delete.php:19 Stack trace: #0 C:\xampp\htdocs\kridha\delete.php(19): PDOStatement->execute() #1 {main} thrown in C:\xampp\htdocs\kridha\delete.php on line 19