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', 'd1v0ilqrg1su29knimrhocdv43', '216.73.216.87', '1765893649', '1765893649', '/index.php?XTCsid=6bac086b61c18464b20a5897fc76826b')

[XT SQL Error]