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', '95c0620f361949ac604801c89e814749', '216.73.216.219', '1772242114', '1772242114', '/shop/shopping_cart.php')

[XT SQL Error]