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', '91o9l6bdvvudkk8aooc06lmu73', '216.73.216.122', '1767788248', '1767788248', '/products_new.php?XTCsid=3547ee950f9337e348e5e07def1466f0')

[XT SQL Error]