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', 'r40ungqger69n74c1irj25c3i7', '216.73.216.147', '1751962003', '1751962003', '/product_info.php?info=p12_33-feet-crape-paper.html&XTCsid=a61b1c7c4e21580bd9d4e85a32d692bc')

[XT SQL Error]