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', '6oliuis5i5t34rp625eu5s63u6', '216.73.216.197', '1751511939', '1751511939', '/popup_content.php?coID=1&XTCsid=1ce6d0a6925740e42ccf6986944a240a')

[XT SQL Error]