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', 'iojr0h3kp6jlepvpj0irll0u33', '216.73.216.244', '1752208661', '1752208661', '/shop_content.php?coID=1&XTCsid=15cbbc13723f7bc63afaf1294f637517')

[XT SQL Error]