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', 'qffubqoca0rg1vlriv94p8t0b1', '54.196.107.247', '1495571214', '1495571214', '/product_info.php?info=p720_Schoene-Toechter.html')

[XT SQL Error]