How to populate custom tables with rows of data

Looking at this article on WP.org it seems you have to create your database first, with some SQL:

function mp_install_table() {
    global $wpdb;

    $table_name = $wpdb->prefix . "countries";

    $sql = "CREATE TABLE $table_name (
        id mediumint(9) NOT NULL AUTO_INCREMENT,
        name tinytext NOT NULL,
        labour_cost INT,
        overheads FLOAT,
        profits FLOAT
    );";

   require_once( ABSPATH . 'wp-admin/includes/upgrade.php' );
   dbDelta( $sql );
}

And after you have your table you can add rows:

function mp_install_country_data() {
    global $wpdb;
    $table_name = $wpdb->prefix . "countries";

    $wpdb->insert(
        $table_name,
        array(
            'id' => '1',
            'name' => 'UK',
            'labour_cost' => '20',
            'overheads' => '0.45',
            'profits' => '0.22'     
        ),

        array(
            'id' => '2',
            'name' =>'China',
            'labour_cost' => '6',
            'overheads' => '0.27',
            'profits' => '0.17'  
        )
    );  
}

I hope this helps.