1366 - Incorrect integer value: '' for column 'customer_id' at row 1

insert into whos_online (customer_id, full_name, session_id, ip_address, time_entry, time_last_click, last_page_url) values ('', 'Guest', 'qe9i6rk8n5fnd6tkl93kf7m4b4', '216.73.216.89', '1760883326', '1760883326', '/xtshop/product_info.php?info=p1113_.html')

[XT SQL Error]