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', 'mpcv3ek8ito27cquaup9je4463', '216.73.216.9', '1758196777', '1758196777', '/index.php?XTCsid=0030a67ff458d3886f5d2b053ac68d0c')

[XT SQL Error]