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', '13tiu4j7mgbq37pl9e720mdkf6', '216.73.216.28', '1764973707', '1764973707', '/popup_content.php?XTCsid=792dd2eece839333bab562194e3fb545&coID=1')

[XT SQL Error]