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', 'nr7ri1h13rbaql2k6artu1cbo1', '216.73.216.9', '1758054415', '1758054415', '/index.php?XTCsid=1d5dd97ce421ec9dee05990fab78bd20')

[XT SQL Error]