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', 'eslonqrus5r8bdd3b6uot66ie2', '216.73.216.9', '1758140249', '1758140249', '/index.php?XTCsid=7b707b7fd087f4e89537b6e7947fb886')

[XT SQL Error]