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', 'a67166e4c361d9f8accf2100819e52e6', '216.73.216.213', '1767296953', '1767296953', '/shop/product_info.php?info=p1_.html')

[XT SQL Error]