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', 'r2rk1ddljvcpc2nft97i6hbi53', '216.73.216.9', '1757819217', '1757819217', '/index.php?XTCsid=78ab7776912f9487a395d4474df042cd')

[XT SQL Error]