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', 'vdns9upg5jb1tc4g51sua39ok4', '216.73.216.174', '1762353643', '1762353643', '/xtshop/product_info.php?info=p981_.html')

[XT SQL Error]