Get customers that bought a product in woocommerce

get_customers_bought_product.php

 function get_customers_bought_product ( $product_id ) {
        global $wpdb;

        return $wpdb->get_results(
            $wpdb->prepare( "
          SELECT postmeta.meta_value as email
          FROM {$wpdb->prefix}woocommerce_order_items as order_items
          LEFT JOIN {$wpdb->prefix}woocommerce_order_itemmeta AS itemmeta ON order_items.order_item_id = itemmeta.order_item_id
          LEFT JOIN {$wpdb->postmeta} AS postmeta ON order_items.order_id = postmeta.post_id
          LEFT JOIN {$wpdb->posts} AS posts ON order_items.order_id = posts.ID
          WHERE
          posts.post_status IN ( 'wc-completed', 'wc-processing' ) AND
          itemmeta.meta_value  = %s AND
          itemmeta.meta_key    IN ( '_variation_id', '_product_id' ) AND
          postmeta.meta_key    IN ( '_billing_email' )
          GROUP BY postmeta.meta_value 
        ", $product_id
            ),
            ARRAY_A
        );
    }