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', 'cv64eh3c9du8h9slp9sh2g3612', '216.73.216.249', '1751514994', '1751514994', '/xtshop/index.php?cat=c17_.html')

[XT SQL Error]