WooCommerce - Add purchased by column in order list

purchased_by_order_column.php

<?php

add_filter( 'manage_shop_order_posts_columns', 'show_purchased_by_shop_order_columns' , 100 );
add_action( 'manage_shop_order_posts_custom_column', 'show_purchased_by_render_shop_order_columns', 2 );
add_filter( 'manage_edit-shop_order_sortable_columns', 'show_purchased_by_shop_order_sortable_columns' );

/**
 * Define custom columns for orders.
 * @param  array $columns
 * @return array
 */
function show_purchased_by_shop_order_columns( $columns ) {
    $columns['purchased_by'] = 'Purchased By';
    return $columns;
}

/**
 * Make columns sortable
 * @param  array $columns
 * @return array
 */
function show_purchased_by_shop_order_sortable_columns( $columns ) {

    $columns['purchased_by'] = 'Purchased By';
    return $columns;

}

/**
 * Output custom columns for coupons.
 * @param string $column
 */
function show_purchased_by_render_shop_order_columns( $column ) {

    if ( $column == 'purchased_by' ) {

        $order    = new WC_Order( get_the_ID() );

        $first_name = $order->billing_first_name;
        $last_name =  $order->billing_last_name;
        $customer_name = $first_name . ' ' . $last_name;
        $customer = get_userdata($order->customer_user);
        $name = $customer->display_name;

        if ( !empty( $customer_name ) ) {

            echo '<a href="'. get_edit_user_link( $order->ID ) .'">'. esc_attr($name ) .'</a>';

        } else {

            echo '<span class="na">–</span>';
            return;

        }

    }

}