WC_Product_Data_Store_CPT::get_product_id_by_sku PHP Method

    public function get_product_id_by_sku($sku)
    {
        global $wpdb;
        return $wpdb->get_var($wpdb->prepare("\n\t\t\tSELECT posts.ID\n\t\t\tFROM {$wpdb->posts} AS posts\n\t\t\tLEFT JOIN {$wpdb->postmeta} AS postmeta ON ( posts.ID = postmeta.post_id )\n\t\t\tWHERE posts.post_type IN ( 'product', 'product_variation' )\n\t\t\tAND postmeta.meta_key = '_sku' AND postmeta.meta_value = '%s'\n\t\t\tLIMIT 1\n\t\t ", $sku));
    }