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', '9qsi62r13aeq90i2h1ais8r3v1', '216.73.216.7', '1758239221', '1758239221', '/index.php?XTCsid=38717c4dd62e88001622b2c7b8b8372a&cat=c6_Foodstuffs.html')

[XT SQL Error]