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', '9f27d1466f86e9952b08052cae9b4a23', '216.73.216.42', '1763354997', '1763354997', '/shop/index.php?cat=c6_.html')

[XT SQL Error]