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', 'dpqpvgkmhum1dt12nqc2ovhap6', '216.73.216.244', '1752218709', '1752218709', '/product_info.php?language=de&info=p14_65-drinking-cups-1-2-Liter.html&XTCsid=a63f52844b6e675f480eaf86612536c2')

[XT SQL Error]