why my tables did not create while activation?

<?php
function createTables(){
         global $wpdb;
        $sql = "create table wp_mainMenu(
           mainMenuId int not null auto_increment primary key,
           title varchar(50),
           showAccordion bit,
           defaultOpen bit,
           priority int
        );# MySQL returned an empty result set (i.e. zero rows).
        create table wp_subMenu(
           subMenuId int not null auto_increment primary key,
           mainMenuId int,
           title varchar(50),
           priority int,
           foreign key(mainMenuId) references mainMenu(mainMenuId) on delete cascade on update cascade
        );
        ";
        require_once( ABSPATH . 'wp-admin/includes/upgrade.php' );
        dbDelta( $sql );

}
register_activation_hook(__FILE__, 'createTables');