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', 'e3f30b0dfb46275fa756f0aeb0f0dc74', '216.73.216.42', '1763440720', '1763440720', '/shop/product_info.php?info=p115_.html')

[XT SQL Error]