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', '14dj1bpn95cpkllntme3c6nf61', '216.73.216.244', '1752202694', '1752202694', '/index.php?XTCsid=ff3f9099e440e42e7d3b08f73df08c38')

[XT SQL Error]