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', 'pjok5g44uo2mh2af71efdq1e21', '216.73.216.165', '1752390993', '1752390993', '/product_info.php?info=p2_Bavarian-Pennant-Chain.html&XTCsid=c407ede434192d8d024c7c2f06b2be8c')

[XT SQL Error]